text: # Copyright 2017 The TensorFlow Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  # ==============================================================================
  """This API defines FeatureColumn abstraction.
  
  FeatureColumns provide a high level abstraction for ingesting and representing
  features. FeatureColumns are also the primary way of encoding features for
  canned @{tf.estimator.Estimator}s.
  
  When using FeatureColumns with `Estimators`, the type of feature column you
  should choose depends on (1) the feature type and (2) the model type.
  
  1. Feature type:
  
    * Continuous features can be represented by `numeric_column`.
    * Categorical features can be represented by any `categorical_column_with_*`
    column:
      - `categorical_column_with_vocabulary_list`
      - `categorical_column_with_vocabulary_file`
      - `categorical_column_with_hash_bucket`
      - `categorical_column_with_identity`
      - `weighted_categorical_column`
  
  2. Model type:
  
    * Deep neural network models (`DNNClassifier`, `DNNRegressor`).
  
      Continuous features can be directly fed into deep neural network models.
  
        age_column = numeric_column("age")
  
      To feed sparse features into DNN models, wrap the column with
      `embedding_column` or `indicator_column`. `indicator_column` is recommended
      for features with only a few possible values. For features with many
      possible values, to reduce the size of your model, `embedding_column` is
      recommended.
  
        embedded_dept_column = embedding_column(
            categorical_column_with_vocabulary_list(
                "department", ["math", "philosophy", ...]), dimension=10)
  
    * Wide (aka linear) models (`LinearClassifier`, `LinearRegressor`).
  
      Sparse features can be fed directly into linear models. They behave like an
      indicator column but with an efficient implementation.
  
        dept_column = categorical_column_with_vocabulary_list("department",
            ["math", "philosophy", "english"])
  
      It is recommended that continuous features be bucketized before being
      fed into linear models.
  
        bucketized_age_column = bucketized_column(
            source_column=age_column,
            boundaries=[18, 25, 30, 35, 40, 45, 50, 55, 60, 65])
  
      Sparse features can be crossed (also known as conjuncted or combined) in
      order to form non-linearities, and then fed into linear models.
  
        cross_dept_age_column = crossed_column(
            columns=["department", bucketized_age_column],
            hash_bucket_size=1000)
  
  Example of building canned `Estimator`s using FeatureColumns:
  
    ```python
    # Define features and transformations
    deep_feature_columns = [age_column, embedded_dept_column]
    wide_feature_columns = [dept_column, bucketized_age_column,
        cross_dept_age_column]
  
    # Build deep model
    estimator = DNNClassifier(
        feature_columns=deep_feature_columns,
        hidden_units=[500, 250, 50])
    estimator.train(...)
  
    # Or build a wide model
    estimator = LinearClassifier(
        feature_columns=wide_feature_columns)
    estimator.train(...)
  
    # Or build a wide and deep model!
    estimator = DNNLinearCombinedClassifier(
        linear_feature_columns=wide_feature_columns,
        dnn_feature_columns=deep_feature_columns,
        dnn_hidden_units=[500, 250, 50])
    estimator.train(...)
    ```
  
  
  FeatureColumns can also be transformed into a generic input layer for
  custom models using `input_layer`.
  
  Example of building model using FeatureColumns, this can be used in a
  `model_fn` which is given to the {tf.estimator.Estimator}:
  
    ```python
    # Building model via layers
  
    deep_feature_columns = [age_column, embedded_dept_column]
    columns_to_tensor = parse_feature_columns_from_examples(
        serialized=my_data,
        feature_columns=deep_feature_columns)
    first_layer = input_layer(
        features=columns_to_tensor,
        feature_columns=deep_feature_columns)
    second_layer = fully_connected(first_layer, ...)
    ```
  
  NOTE: Functions prefixed with "_" indicate experimental or private parts of
  the API subject to change, and should not be relied upon!
  """
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import abc
  import collections
  import math
  
  import numpy as np
  import six
  
  
  from tensorflow.python.eager import context
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import sparse_tensor as sparse_tensor_lib
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.keras._impl.keras.engine import training
  from tensorflow.python.layers import base
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import check_ops
  from tensorflow.python.ops import control_flow_ops
  from tensorflow.python.ops import embedding_ops
  from tensorflow.python.ops import init_ops
  from tensorflow.python.ops import lookup_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn_ops
  from tensorflow.python.ops import parsing_ops
  from tensorflow.python.ops import resource_variable_ops
  from tensorflow.python.ops import sparse_ops
  from tensorflow.python.ops import string_ops
  from tensorflow.python.ops import template
  from tensorflow.python.ops import variable_scope
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import gfile
  from tensorflow.python.platform import tf_logging as logging
  from tensorflow.python.training import checkpoint_utils
  from tensorflow.python.util import nest
  from tensorflow.python.util.tf_export import tf_export
  
  
  def _internal_input_layer(features,
                            feature_columns,
                            weight_collections=None,
                            trainable=True,
                            cols_to_vars=None,
                            scope=None):
    """See input_layer. `scope` is a name or variable scope to use."""
  
    feature_columns = _clean_feature_columns(feature_columns)
    for column in feature_columns:
      if not isinstance(column, _DenseColumn):
        raise ValueError(
            'Items of feature_columns must be a _DenseColumn. '
            'You can wrap a categorical column with an '
            'embedding_column or indicator_column. Given: {}'.format(column))
    weight_collections = list(weight_collections or [])
    if ops.GraphKeys.GLOBAL_VARIABLES not in weight_collections:
      weight_collections.append(ops.GraphKeys.GLOBAL_VARIABLES)
    if ops.GraphKeys.MODEL_VARIABLES not in weight_collections:
      weight_collections.append(ops.GraphKeys.MODEL_VARIABLES)
  
    # a non-None `scope` can allow for variable reuse, when, e.g., this function
    # is wrapped by a `make_template`.
    with variable_scope.variable_scope(
        scope, default_name='input_layer', values=features.values()):
      builder = _LazyBuilder(features)
      output_tensors = []
      ordered_columns = []
      for column in sorted(feature_columns, key=lambda x: x.name):
        ordered_columns.append(column)
        with variable_scope.variable_scope(
            None, default_name=column._var_scope_name):  # pylint: disable=protected-access
          tensor = column._get_dense_tensor(  # pylint: disable=protected-access
              builder,
              weight_collections=weight_collections,
              trainable=trainable)
          num_elements = column._variable_shape.num_elements()  # pylint: disable=protected-access
          batch_size = array_ops.shape(tensor)[0]
          output_tensors.append(
              array_ops.reshape(tensor, shape=(batch_size, num_elements)))
          if cols_to_vars is not None:
            # Retrieve any variables created (some _DenseColumn's don't create
            # variables, in which case an empty list is returned).
            cols_to_vars[column] = ops.get_collection(
                ops.GraphKeys.GLOBAL_VARIABLES,
                scope=variable_scope.get_variable_scope().name)
      _verify_static_batch_size_equality(output_tensors, ordered_columns)
      return array_ops.concat(output_tensors, 1)
  
  
  @tf_export('feature_column.input_layer')
  def input_layer(features,
                  feature_columns,
                  weight_collections=None,
                  trainable=True,
                  cols_to_vars=None):
    """Returns a dense `Tensor` as input layer based on given `feature_columns`.
  
    Generally a single example in training data is described with FeatureColumns.
    At the first layer of the model, this column oriented data should be converted
    to a single `Tensor`.
  
    Example:
  
    ```python
    price = numeric_column('price')
    keywords_embedded = embedding_column(
        categorical_column_with_hash_bucket("keywords", 10K), dimensions=16)
    columns = [price, keywords_embedded, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
    for units in [128, 64, 32]:
      dense_tensor = tf.layers.dense(dense_tensor, units, tf.nn.relu)
    prediction = tf.layers.dense(dense_tensor, 1)
    ```
  
    Args:
      features: A mapping from key to tensors. `_FeatureColumn`s look up via these
        keys. For example `numeric_column('price')` will look at 'price' key in
        this dict. Values can be a `SparseTensor` or a `Tensor` depends on
        corresponding `_FeatureColumn`.
      feature_columns: An iterable containing the FeatureColumns to use as inputs
        to your model. All items should be instances of classes derived from
        `_DenseColumn` such as `numeric_column`, `embedding_column`,
        `bucketized_column`, `indicator_column`. If you have categorical features,
        you can wrap them with an `embedding_column` or `indicator_column`.
      weight_collections: A list of collection names to which the Variable will be
        added. Note that variables will also be added to collections
        `tf.GraphKeys.GLOBAL_VARIABLES` and `ops.GraphKeys.MODEL_VARIABLES`.
      trainable: If `True` also add the variable to the graph collection
        `GraphKeys.TRAINABLE_VARIABLES` (see `tf.Variable`).
      cols_to_vars: If not `None`, must be a dictionary that will be filled with a
        mapping from `_FeatureColumn` to list of `Variable`s.  For example, after
        the call, we might have cols_to_vars =
        {_EmbeddingColumn(
          categorical_column=_HashedCategoricalColumn(
            key='sparse_feature', hash_bucket_size=5, dtype=tf.string),
          dimension=10): [<tf.Variable 'some_variable:0' shape=(5, 10),
                          <tf.Variable 'some_variable:1' shape=(5, 10)]}
        If a column creates no variables, its value will be an empty list.
  
    Returns:
      A `Tensor` which represents input layer of a model. Its shape
      is (batch_size, first_layer_dimension) and its dtype is `float32`.
      first_layer_dimension is determined based on given `feature_columns`.
  
    Raises:
      ValueError: if an item in `feature_columns` is not a `_DenseColumn`.
    """
    return _internal_input_layer(features, feature_columns, weight_collections,
                                 trainable, cols_to_vars)
  
  
  # TODO(akshayka): InputLayer should be a subclass of Layer, and it
  # should implement the logic in input_layer using Layer's build-and-call
  # paradigm; input_layer should create an instance of InputLayer and
  # return the result of invoking its apply method, just as functional layers do.
  class InputLayer(object):
    """An object-oriented version of `input_layer` that reuses variables."""
  
    def __init__(self,
                 feature_columns,
                 weight_collections=None,
                 trainable=True,
                 cols_to_vars=None):
      """See `input_layer`."""
  
      self._feature_columns = feature_columns
      self._weight_collections = weight_collections
      self._trainable = trainable
      self._cols_to_vars = cols_to_vars
      self._input_layer_template = template.make_template(
          'feature_column_input_layer',
          _internal_input_layer,
          create_scope_now_=True)
      self._scope = self._input_layer_template.variable_scope
  
    def __call__(self, features):
      return self._input_layer_template(
          features=features,
          feature_columns=self._feature_columns,
          weight_collections=self._weight_collections,
          trainable=self._trainable,
          cols_to_vars=None,
          scope=self._scope)
  
    @property
    def non_trainable_variables(self):
      return self._input_layer_template.non_trainable_variables
  
    @property
    def non_trainable_weights(self):
      return self._input_layer_template.non_trainable_weights
  
    @property
    def trainable_variables(self):
      return self._input_layer_template.trainable_variables
  
    @property
    def trainable_weights(self):
      return self._input_layer_template.trainable_weights
  
    @property
    def variables(self):
      return self._input_layer_template.variables
  
    @property
    def weights(self):
      return self._input_layer_template.weights
  
  
  @tf_export('feature_column.linear_model')
  def linear_model(features,
                   feature_columns,
                   units=1,
                   sparse_combiner='sum',
                   weight_collections=None,
                   trainable=True,
                   cols_to_vars=None):
    """Returns a linear prediction `Tensor` based on given `feature_columns`.
  
    This function generates a weighted sum based on output dimension `units`.
    Weighted sum refers to logits in classification problems. It refers to the
    prediction itself for linear regression problems.
  
    Note on supported columns: `linear_model` treats categorical columns as
    `indicator_column`s while `input_layer` explicitly requires wrapping each
    of them with an `embedding_column` or an `indicator_column`.
  
    Example:
  
    ```python
    price = numeric_column('price')
    price_buckets = bucketized_column(price, boundaries=[0., 10., 100., 1000.])
    keywords = categorical_column_with_hash_bucket("keywords", 10K)
    keywords_price = crossed_column('keywords', price_buckets, ...)
    columns = [price_buckets, keywords, keywords_price ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    prediction = linear_model(features, columns)
    ```
  
    Args:
      features: A mapping from key to tensors. `_FeatureColumn`s look up via these
        keys. For example `numeric_column('price')` will look at 'price' key in
        this dict. Values are `Tensor` or `SparseTensor` depending on
        corresponding `_FeatureColumn`.
      feature_columns: An iterable containing the FeatureColumns to use as inputs
        to your model. All items should be instances of classes derived from
        `_FeatureColumn`s.
      units: An integer, dimensionality of the output space. Default value is 1.
      sparse_combiner: A string specifying how to reduce if a sparse column is
        multivalent. Currently "mean", "sqrtn" and "sum" are supported, with "sum"
        the default. "sqrtn" often achieves good accuracy, in particular with
        bag-of-words columns. It combines each sparse columns independently.
          * "sum": do not normalize features in the column
          * "mean": do l1 normalization on features in the column
          * "sqrtn": do l2 normalization on features in the column
      weight_collections: A list of collection names to which the Variable will be
        added. Note that, variables will also be added to collections
        `tf.GraphKeys.GLOBAL_VARIABLES` and `ops.GraphKeys.MODEL_VARIABLES`.
      trainable: If `True` also add the variable to the graph collection
        `GraphKeys.TRAINABLE_VARIABLES` (see `tf.Variable`).
      cols_to_vars: If not `None`, must be a dictionary that will be filled with a
        mapping from `_FeatureColumn` to associated list of `Variable`s.  For
        example, after the call, we might have cols_to_vars = {
          _NumericColumn(
            key='numeric_feature1', shape=(1,):
          [<tf.Variable 'linear_model/price2/weights:0' shape=(1, 1)>],
          'bias': [<tf.Variable 'linear_model/bias_weights:0' shape=(1,)>],
          _NumericColumn(
            key='numeric_feature2', shape=(2,)):
          [<tf.Variable 'linear_model/price1/weights:0' shape=(2, 1)>]}
        If a column creates no variables, its value will be an empty list. Note
        that cols_to_vars will also contain a string key 'bias' that maps to a
        list of Variables.
  
    Returns:
      A `Tensor` which represents predictions/logits of a linear model. Its shape
      is (batch_size, units) and its dtype is `float32`.
  
    Raises:
      ValueError: if an item in `feature_columns` is neither a `_DenseColumn`
        nor `_CategoricalColumn`.
    """
    linear_model_layer = _LinearModel(
        feature_columns=feature_columns,
        units=units,
        sparse_combiner=sparse_combiner,
        weight_collections=weight_collections,
        trainable=trainable,
        name='linear_model')
    retval = linear_model_layer(features)  # pylint: disable=not-callable
    if cols_to_vars is not None:
      cols_to_vars.update(linear_model_layer.cols_to_vars())
    return retval
  
  
  def _add_to_collections(var, weight_collections):
    # TODO(rohanj): Explore adding a _get_variable_list method on `Variable`
    # so that we don't have to do this check.
    if isinstance(var, variables.PartitionedVariable):
      for constituent_var in list(var):
        ops.add_to_collections(weight_collections, constituent_var)
    else:
      ops.add_to_collections(weight_collections, var)
  
  
  class _FCLinearWrapper(base.Layer):
    """Wraps a _FeatureColumn in a layer for use in a linear model.
  
    See `linear_model` above.
    """
  
    def __init__(self,
                 feature_column,
                 units=1,
                 sparse_combiner='sum',
                 weight_collections=None,
                 trainable=True,
                 name=None,
                 **kwargs):
      super(_FCLinearWrapper, self).__init__(
          trainable=trainable, name=name, **kwargs)
      self._feature_column = feature_column
      self._units = units
      self._sparse_combiner = sparse_combiner
      self._weight_collections = weight_collections
  
    def build(self, _):
      if isinstance(self._feature_column, _CategoricalColumn):
        weight = self.add_variable(
            name='weights',
            shape=(self._feature_column._num_buckets, self._units),  # pylint: disable=protected-access
            initializer=init_ops.zeros_initializer(),
            trainable=self.trainable)
      else:
        num_elements = self._feature_column._variable_shape.num_elements()  # pylint: disable=protected-access
        weight = self.add_variable(
            name='weights',
            shape=[num_elements, self._units],
            initializer=init_ops.zeros_initializer(),
            trainable=self.trainable)
      _add_to_collections(weight, self._weight_collections)
      self._weight_var = weight
      self.built = True
  
    def call(self, builder):
      weighted_sum = _create_weighted_sum(
          column=self._feature_column,
          builder=builder,
          units=self._units,
          sparse_combiner=self._sparse_combiner,
          weight_collections=self._weight_collections,
          trainable=self.trainable,
          weight_var=self._weight_var)
      return weighted_sum
  
  
  class _BiasLayer(base.Layer):
    """A layer for the bias term.
    """
  
    def __init__(self,
                 units=1,
                 trainable=True,
                 weight_collections=None,
                 name=None,
                 **kwargs):
      super(_BiasLayer, self).__init__(trainable=trainable, name=name, **kwargs)
      self._units = units
      self._weight_collections = weight_collections
  
    def build(self, _):
      self._bias_variable = self.add_variable(
          'bias_weights',
          shape=[self._units],
          initializer=init_ops.zeros_initializer(),
          trainable=self.trainable)
      _add_to_collections(self._bias_variable, self._weight_collections)
      self.built = True
  
    def call(self, _):
      return self._bias_variable
  
  
  def _get_expanded_variable_list(variable):
    if (isinstance(variable, variables.Variable) or
        resource_variable_ops.is_resource_variable(variable)):
      return [variable]  # Single variable case.
    else:  # Must be a PartitionedVariable, so convert into a list.
      return list(variable)
  
  
  def _strip_leading_slashes(name):
    return name.rsplit('/', 1)[-1]
  
  
  class _LinearModel(training.Model):
    """Creates a linear model using feature columns.
  
    See `linear_model` for details.
    """
  
    def __init__(self,
                 feature_columns,
                 units=1,
                 sparse_combiner='sum',
                 weight_collections=None,
                 trainable=True,
                 name=None,
                 **kwargs):
      super(_LinearModel, self).__init__(name=name, **kwargs)
      self._feature_columns = _clean_feature_columns(feature_columns)
      self._weight_collections = list(weight_collections or [])
      if ops.GraphKeys.MODEL_VARIABLES not in self._weight_collections:
        self._weight_collections.append(ops.GraphKeys.MODEL_VARIABLES)
  
      column_layers = {}
      for column in sorted(self._feature_columns, key=lambda x: x.name):
        with variable_scope.variable_scope(
            None, default_name=column._var_scope_name) as vs:  # pylint: disable=protected-access
          # Having the fully expressed variable scope name ends up doubly
          # expressing the outer scope (scope with which this method was called)
          # in the name of the variable that would get created.
          column_name = _strip_leading_slashes(vs.name)
        column_layer = _FCLinearWrapper(column, units, sparse_combiner,
                                        self._weight_collections, trainable,
                                        column_name, **kwargs)
        column_layers[column_name] = column_layer
      self._column_layers = self._add_layers(column_layers)
      self._bias_layer = _BiasLayer(
          units=units,
          trainable=trainable,
          weight_collections=self._weight_collections,
          name='bias_layer',
          **kwargs)
      self._cols_to_vars = {}
  
    def cols_to_vars(self):
      """Returns a dict mapping _FeatureColumns to variables.
  
      See `linear_model` for more information.
      This is not populated till `call` is called i.e. layer is built.
      """
      return self._cols_to_vars
  
    def call(self, features):
      with variable_scope.variable_scope(self.name):
        for column in self._feature_columns:
          if not isinstance(column, (_DenseColumn, _CategoricalColumn)):
            raise ValueError(
                'Items of feature_columns must be either a '
                '_DenseColumn or _CategoricalColumn. Given: {}'.format(column))
        weighted_sums = []
        ordered_columns = []
        builder = _LazyBuilder(features)
        for layer in sorted(self._column_layers.values(), key=lambda x: x.name):
          column = layer._feature_column  # pylint: disable=protected-access
          ordered_columns.append(column)
          weighted_sum = layer(builder)
          weighted_sums.append(weighted_sum)
          self._cols_to_vars[column] = ops.get_collection(
              ops.GraphKeys.GLOBAL_VARIABLES, scope=layer.scope_name)
  
        _verify_static_batch_size_equality(weighted_sums, ordered_columns)
        predictions_no_bias = math_ops.add_n(
            weighted_sums, name='weighted_sum_no_bias')
        predictions = nn_ops.bias_add(
            predictions_no_bias,
            self._bias_layer(  # pylint: disable=not-callable
                builder,
                scope=variable_scope.get_variable_scope()),  # pylint: disable=not-callable
            name='weighted_sum')
        bias = self._bias_layer.variables[0]
        self._cols_to_vars['bias'] = _get_expanded_variable_list(bias)
      return predictions
  
    def _add_layers(self, layers):
      # "Magic" required for keras.Model classes to track all the variables in
      # a list of layers.Layer objects.
      # TODO(ashankar): Figure out API so user code doesn't have to do this.
      for name, layer in layers.items():
        setattr(self, 'layer-%s' % name, layer)
      return layers
  
  
  def _transform_features(features, feature_columns):
    """Returns transformed features based on features columns passed in.
  
    Please note that most probably you would not need to use this function. Please
    check `input_layer` and `linear_model` to see whether they will
    satisfy your use case or not.
  
    Example:
  
    ```python
    # Define features and transformations
    crosses_a_x_b = crossed_column(
        columns=["sparse_feature_a", "sparse_feature_b"], hash_bucket_size=10000)
    price_buckets = bucketized_column(
        source_column=numeric_column("price"), boundaries=[...])
  
    columns = [crosses_a_x_b, price_buckets]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    transformed = transform_features(features=features, feature_columns=columns)
  
    assertCountEqual(columns, transformed.keys())
    ```
  
    Args:
      features: A mapping from key to tensors. `_FeatureColumn`s look up via these
        keys. For example `numeric_column('price')` will look at 'price' key in
        this dict. Values can be a `SparseTensor` or a `Tensor` depends on
        corresponding `_FeatureColumn`.
      feature_columns: An iterable containing all the `_FeatureColumn`s.
  
    Returns:
      A `dict` mapping `_FeatureColumn` to `Tensor` and `SparseTensor` values.
    """
    feature_columns = _clean_feature_columns(feature_columns)
    outputs = {}
    with ops.name_scope(
        None, default_name='transform_features', values=features.values()):
      builder = _LazyBuilder(features)
      for column in sorted(feature_columns, key=lambda x: x.name):
        with ops.name_scope(None, default_name=column.name):
          outputs[column] = builder.get(column)
    return outputs
  
  
  @tf_export('feature_column.make_parse_example_spec')
  def make_parse_example_spec(feature_columns):
    """Creates parsing spec dictionary from input feature_columns.
  
    The returned dictionary can be used as arg 'features' in `tf.parse_example`.
  
    Typical usage example:
  
    ```python
    # Define features and transformations
    feature_a = categorical_column_with_vocabulary_file(...)
    feature_b = numeric_column(...)
    feature_c_bucketized = bucketized_column(numeric_column("feature_c"), ...)
    feature_a_x_feature_c = crossed_column(
        columns=["feature_a", feature_c_bucketized], ...)
  
    feature_columns = set(
        [feature_b, feature_c_bucketized, feature_a_x_feature_c])
    features = tf.parse_example(
        serialized=serialized_examples,
        features=make_parse_example_spec(feature_columns))
    ```
  
    For the above example, make_parse_example_spec would return the dict:
  
    ```python
    {
        "feature_a": parsing_ops.VarLenFeature(tf.string),
        "feature_b": parsing_ops.FixedLenFeature([1], dtype=tf.float32),
        "feature_c": parsing_ops.FixedLenFeature([1], dtype=tf.float32)
    }
    ```
  
    Args:
      feature_columns: An iterable containing all feature columns. All items
        should be instances of classes derived from `_FeatureColumn`.
  
    Returns:
      A dict mapping each feature key to a `FixedLenFeature` or `VarLenFeature`
      value.
  
    Raises:
      ValueError: If any of the given `feature_columns` is not a `_FeatureColumn`
        instance.
    """
    result = {}
    for column in feature_columns:
      if not isinstance(column, _FeatureColumn):
        raise ValueError(
            'All feature_columns must be _FeatureColumn instances. '
            'Given: {}'.format(column))
      config = column._parse_example_spec  # pylint: disable=protected-access
      for key, value in six.iteritems(config):
        if key in result and value != result[key]:
          raise ValueError(
              'feature_columns contain different parse_spec for key '
              '{}. Given {} and {}'.format(key, value, result[key]))
      result.update(config)
    return result
  
  
  @tf_export('feature_column.embedding_column')
  def embedding_column(
      categorical_column, dimension, combiner='mean', initializer=None,
      ckpt_to_load_from=None, tensor_name_in_ckpt=None, max_norm=None,
      trainable=True):
    """`_DenseColumn` that converts from sparse, categorical input.
  
    Use this when your inputs are sparse, but you want to convert them to a dense
    representation (e.g., to feed to a DNN).
  
    Inputs must be a `_CategoricalColumn` created by any of the
    `categorical_column_*` function. Here is an example of using
    `embedding_column` with `DNNClassifier`:
  
    ```python
    video_id = categorical_column_with_identity(
        key='video_id', num_buckets=1000000, default_value=0)
    columns = [embedding_column(video_id, 9),...]
  
    estimator = tf.estimator.DNNClassifier(feature_columns=columns, ...)
  
    label_column = ...
    def input_fn():
      features = tf.parse_example(
          ..., features=make_parse_example_spec(columns + [label_column]))
      labels = features.pop(label_column.name)
      return features, labels
  
    estimator.train(input_fn=input_fn, steps=100)
    ```
  
    Here is an example using `embedding_column` with model_fn:
  
    ```python
    def model_fn(features, ...):
      video_id = categorical_column_with_identity(
          key='video_id', num_buckets=1000000, default_value=0)
      columns = [embedding_column(video_id, 9),...]
      dense_tensor = input_layer(features, columns)
      # Form DNN layers, calculate loss, and return EstimatorSpec.
      ...
    ```
  
    Args:
      categorical_column: A `_CategoricalColumn` created by a
        `categorical_column_with_*` function. This column produces the sparse IDs
        that are inputs to the embedding lookup.
      dimension: An integer specifying dimension of the embedding, must be > 0.
      combiner: A string specifying how to reduce if there are multiple entries
        in a single row. Currently 'mean', 'sqrtn' and 'sum' are supported, with
        'mean' the default. 'sqrtn' often achieves good accuracy, in particular
        with bag-of-words columns. Each of this can be thought as example level
        normalizations on the column. For more information, see
        `tf.embedding_lookup_sparse`.
      initializer: A variable initializer function to be used in embedding
        variable initialization. If not specified, defaults to
        `tf.truncated_normal_initializer` with mean `0.0` and standard deviation
        `1/sqrt(dimension)`.
      ckpt_to_load_from: String representing checkpoint name/pattern from which to
        restore column weights. Required if `tensor_name_in_ckpt` is not `None`.
      tensor_name_in_ckpt: Name of the `Tensor` in `ckpt_to_load_from` from
        which to restore the column weights. Required if `ckpt_to_load_from` is
        not `None`.
      max_norm: If not `None`, embedding values are l2-normalized to this value.
      trainable: Whether or not the embedding is trainable. Default is True.
  
    Returns:
      `_DenseColumn` that converts from sparse input.
  
    Raises:
      ValueError: if `dimension` not > 0.
      ValueError: if exactly one of `ckpt_to_load_from` and `tensor_name_in_ckpt`
        is specified.
      ValueError: if `initializer` is specified and is not callable.
      RuntimeError: If eager execution is enabled.
    """
    if (dimension is None) or (dimension < 1):
      raise ValueError('Invalid dimension {}.'.format(dimension))
    if (ckpt_to_load_from is None) != (tensor_name_in_ckpt is None):
      raise ValueError('Must specify both `ckpt_to_load_from` and '
                       '`tensor_name_in_ckpt` or none of them.')
  
    if (initializer is not None) and (not callable(initializer)):
      raise ValueError('initializer must be callable if specified. '
                       'Embedding of column_name: {}'.format(
                           categorical_column.name))
    if initializer is None:
      initializer = init_ops.truncated_normal_initializer(
          mean=0.0, stddev=1 / math.sqrt(dimension))
  
    embedding_shape = categorical_column._num_buckets, dimension  # pylint: disable=protected-access
  
    def _creator(weight_collections, scope):
      embedding_column_layer = _EmbeddingColumnLayer(
          embedding_shape=embedding_shape,
          initializer=initializer,
          weight_collections=weight_collections,
          trainable=trainable,
          name='embedding_column_layer')
      return embedding_column_layer(None, scope=scope)  # pylint: disable=not-callable
  
    return _EmbeddingColumn(
        categorical_column=categorical_column,
        dimension=dimension,
        combiner=combiner,
        layer_creator=_creator,
        ckpt_to_load_from=ckpt_to_load_from,
        tensor_name_in_ckpt=tensor_name_in_ckpt,
        max_norm=max_norm,
        trainable=trainable)
  
  
  @tf_export('feature_column.shared_embedding_columns')
  def shared_embedding_columns(
      categorical_columns, dimension, combiner='mean', initializer=None,
      shared_embedding_collection_name=None, ckpt_to_load_from=None,
      tensor_name_in_ckpt=None, max_norm=None, trainable=True):
    """List of dense columns that convert from sparse, categorical input.
  
    This is similar to `embedding_column`, except that it produces a list of
    embedding columns that share the same embedding weights.
  
    Use this when your inputs are sparse and of the same type (e.g. watched and
    impression video IDs that share the same vocabulary), and you want to convert
    them to a dense representation (e.g., to feed to a DNN).
  
    Inputs must be a list of categorical columns created by any of the
    `categorical_column_*` function. They must all be of the same type and have
    the same arguments except `key`. E.g. they can be
    categorical_column_with_vocabulary_file with the same vocabulary_file. Some or
    all columns could also be weighted_categorical_column.
  
    Here is an example embedding of two features for a DNNClassifier model:
  
    ```python
    watched_video_id = categorical_column_with_vocabulary_file(
        'watched_video_id', video_vocabulary_file, video_vocabulary_size)
    impression_video_id = categorical_column_with_vocabulary_file(
        'impression_video_id', video_vocabulary_file, video_vocabulary_size)
    columns = shared_embedding_columns(
        [watched_video_id, impression_video_id], dimension=10)
  
    estimator = tf.estimator.DNNClassifier(feature_columns=columns, ...)
  
    label_column = ...
    def input_fn():
      features = tf.parse_example(
          ..., features=make_parse_example_spec(columns + [label_column]))
      labels = features.pop(label_column.name)
      return features, labels
  
    estimator.train(input_fn=input_fn, steps=100)
    ```
  
    Here is an example using `shared_embedding_columns` with model_fn:
  
    ```python
    def model_fn(features, ...):
      watched_video_id = categorical_column_with_vocabulary_file(
          'watched_video_id', video_vocabulary_file, video_vocabulary_size)
      impression_video_id = categorical_column_with_vocabulary_file(
          'impression_video_id', video_vocabulary_file, video_vocabulary_size)
      columns = shared_embedding_columns(
          [watched_video_id, impression_video_id], dimension=10)
      dense_tensor = input_layer(features, columns)
      # Form DNN layers, calculate loss, and return EstimatorSpec.
      ...
    ```
  
    Args:
      categorical_columns: List of categorical columns created by a
        `categorical_column_with_*` function. These columns produce the sparse IDs
        that are inputs to the embedding lookup. All columns must be of the same
        type and have the same arguments except `key`. E.g. they can be
        categorical_column_with_vocabulary_file with the same vocabulary_file.
        Some or all columns could also be weighted_categorical_column.
      dimension: An integer specifying dimension of the embedding, must be > 0.
      combiner: A string specifying how to reduce if there are multiple entries
        in a single row. Currently 'mean', 'sqrtn' and 'sum' are supported, with
        'mean' the default. 'sqrtn' often achieves good accuracy, in particular
        with bag-of-words columns. Each of this can be thought as example level
        normalizations on the column. For more information, see
        `tf.embedding_lookup_sparse`.
      initializer: A variable initializer function to be used in embedding
        variable initialization. If not specified, defaults to
        `tf.truncated_normal_initializer` with mean `0.0` and standard deviation
        `1/sqrt(dimension)`.
      shared_embedding_collection_name: Optional name of the collection where
        shared embedding weights are added. If not given, a reasonable name will
        be chosen based on the names of `categorical_columns`. This is also used
        in `variable_scope` when creating shared embedding weights.
      ckpt_to_load_from: String representing checkpoint name/pattern from which to
        restore column weights. Required if `tensor_name_in_ckpt` is not `None`.
      tensor_name_in_ckpt: Name of the `Tensor` in `ckpt_to_load_from` from
        which to restore the column weights. Required if `ckpt_to_load_from` is
        not `None`.
      max_norm: If not `None`, embedding values are l2-normalized to this value.
      trainable: Whether or not the embedding is trainable. Default is True.
  
    Returns:
      A list of dense columns that converts from sparse input. The order of
      results follows the ordering of `categorical_columns`.
  
    Raises:
      ValueError: if `dimension` not > 0.
      ValueError: if any of the given `categorical_columns` is of different type
        or has different arguments than the others.
      ValueError: if exactly one of `ckpt_to_load_from` and `tensor_name_in_ckpt`
        is specified.
      ValueError: if `initializer` is specified and is not callable.
    """
    if (dimension is None) or (dimension < 1):
      raise ValueError('Invalid dimension {}.'.format(dimension))
    if (ckpt_to_load_from is None) != (tensor_name_in_ckpt is None):
      raise ValueError('Must specify both `ckpt_to_load_from` and '
                       '`tensor_name_in_ckpt` or none of them.')
  
    if (initializer is not None) and (not callable(initializer)):
      raise ValueError('initializer must be callable if specified.')
    if initializer is None:
      initializer = init_ops.truncated_normal_initializer(
          mean=0.0, stddev=1. / math.sqrt(dimension))
  
    # Sort the columns so the default collection name is deterministic even if the
    # user passes columns from an unsorted collection, such as dict.values().
    sorted_columns = sorted(categorical_columns, key=lambda x: x.name)
  
    c0 = sorted_columns[0]
    num_buckets = c0._num_buckets  # pylint: disable=protected-access
    if not isinstance(c0, _CategoricalColumn):
      raise ValueError(
          'All categorical_columns must be subclasses of _CategoricalColumn. '
          'Given: {}, of type: {}'.format(c0, type(c0)))
    if isinstance(c0, _WeightedCategoricalColumn):
      c0 = c0.categorical_column
    for c in sorted_columns[1:]:
      if isinstance(c, _WeightedCategoricalColumn):
        c = c.categorical_column
      if not isinstance(c, type(c0)):
        raise ValueError(
            'To use shared_embedding_column, all categorical_columns must have '
            'the same type, or be weighted_categorical_column of the same type. '
            'Given column: {} of type: {} does not match given column: {} of '
            'type: {}'.format(c0, type(c0), c, type(c)))
      if num_buckets != c._num_buckets:  # pylint: disable=protected-access
        raise ValueError(
            'To use shared_embedding_column, all categorical_columns must have '
            'the same number of buckets. Given column: {} with buckets: {} does  '
            'not match column: {} with buckets: {}'.format(
                c0, num_buckets, c, c._num_buckets))  # pylint: disable=protected-access
  
    if not shared_embedding_collection_name:
      shared_embedding_collection_name = '_'.join(c.name for c in sorted_columns)
      shared_embedding_collection_name += '_shared_embedding'
  
    # Create the state (_SharedEmbeddingColumnLayer) here.
    embedding_shape = num_buckets, dimension
  
    shared_embedding_column_layer = _EmbeddingColumnLayer(
        embedding_shape=embedding_shape,
        initializer=initializer,
        weight_collections=[],
        trainable=trainable,
        name=shared_embedding_collection_name)
  
    result = []
    for column in categorical_columns:
      result.append(
          _SharedEmbeddingColumn(
              categorical_column=column,
              initializer=initializer,
              dimension=dimension,
              combiner=combiner,
              var_scope_name=shared_embedding_collection_name,
              ckpt_to_load_from=ckpt_to_load_from,
              tensor_name_in_ckpt=tensor_name_in_ckpt,
              max_norm=max_norm,
              trainable=trainable))
  
    for single_result in result:
      single_result._set_layer(shared_embedding_column_layer)  # pylint: disable=protected-access
      single_result._set_all_columns(result)  # pylint: disable=protected-access
  
    return result
  
  
  @tf_export('feature_column.numeric_column')
  def numeric_column(key,
                     shape=(1,),
                     default_value=None,
                     dtype=dtypes.float32,
                     normalizer_fn=None):
    """Represents real valued or numerical features.
  
    Example:
  
    ```python
    price = numeric_column('price')
    columns = [price, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
  
    # or
    bucketized_price = bucketized_column(price, boundaries=[...])
    columns = [bucketized_price, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
    ```
  
    Args:
      key: A unique string identifying the input feature. It is used as the
        column name and the dictionary key for feature parsing configs, feature
        `Tensor` objects, and feature columns.
      shape: An iterable of integers specifies the shape of the `Tensor`. An
        integer can be given which means a single dimension `Tensor` with given
        width. The `Tensor` representing the column will have the shape of
        [batch_size] + `shape`.
      default_value: A single value compatible with `dtype` or an iterable of
        values compatible with `dtype` which the column takes on during
        `tf.Example` parsing if data is missing. A default value of `None` will
        cause `tf.parse_example` to fail if an example does not contain this
        column. If a single value is provided, the same value will be applied as
        the default value for every item. If an iterable of values is provided,
        the shape of the `default_value` should be equal to the given `shape`.
      dtype: defines the type of values. Default value is `tf.float32`. Must be a
        non-quantized, real integer or floating point type.
      normalizer_fn: If not `None`, a function that can be used to normalize the
        value of the tensor after `default_value` is applied for parsing.
        Normalizer function takes the input `Tensor` as its argument, and returns
        the output `Tensor`. (e.g. lambda x: (x - 3.0) / 4.2). Please note that
        even though the most common use case of this function is normalization, it
        can be used for any kind of Tensorflow transformations.
  
    Returns:
      A `_NumericColumn`.
  
    Raises:
      TypeError: if any dimension in shape is not an int
      ValueError: if any dimension in shape is not a positive integer
      TypeError: if `default_value` is an iterable but not compatible with `shape`
      TypeError: if `default_value` is not compatible with `dtype`.
      ValueError: if `dtype` is not convertible to `tf.float32`.
    """
    shape = _check_shape(shape, key)
    if not (dtype.is_integer or dtype.is_floating):
      raise ValueError('dtype must be convertible to float. '
                       'dtype: {}, key: {}'.format(dtype, key))
    default_value = _check_default_value(shape, default_value, dtype, key)
  
    if normalizer_fn is not None and not callable(normalizer_fn):
      raise TypeError(
          'normalizer_fn must be a callable. Given: {}'.format(normalizer_fn))
  
    return _NumericColumn(
        key,
        shape=shape,
        default_value=default_value,
        dtype=dtype,
        normalizer_fn=normalizer_fn)
  
  
  @tf_export('feature_column.bucketized_column')
  def bucketized_column(source_column, boundaries):
    """Represents discretized dense input.
  
    Buckets include the left boundary, and exclude the right boundary. Namely,
    `boundaries=[0., 1., 2.]` generates buckets `(-inf, 0.)`, `[0., 1.)`,
    `[1., 2.)`, and `[2., +inf)`.
  
    For example, if the inputs are
  
    ```python
    boundaries = [0, 10, 100]
    input tensor = [[-5, 10000]
                    [150,   10]
                    [5,    100]]
    ```
  
    then the output will be
  
    ```python
    output = [[0, 3]
              [3, 2]
              [1, 3]]
    ```
  
    Example:
  
    ```python
    price = numeric_column('price')
    bucketized_price = bucketized_column(price, boundaries=[...])
    columns = [bucketized_price, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
  
    # or
    columns = [bucketized_price, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
    ```
  
    `bucketized_column` can also be crossed with another categorical column using
    `crossed_column`:
  
    ```python
    price = numeric_column('price')
    # bucketized_column converts numerical feature to a categorical one.
    bucketized_price = bucketized_column(price, boundaries=[...])
    # 'keywords' is a string feature.
    price_x_keywords = crossed_column([bucketized_price, 'keywords'], 50K)
    columns = [price_x_keywords, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
    ```
  
    Args:
      source_column: A one-dimensional dense column which is generated with
        `numeric_column`.
      boundaries: A sorted list or tuple of floats specifying the boundaries.
  
    Returns:
      A `_BucketizedColumn`.
  
    Raises:
      ValueError: If `source_column` is not a numeric column, or if it is not
        one-dimensional.
      ValueError: If `boundaries` is not a sorted list or tuple.
    """
    if not isinstance(source_column, _NumericColumn):
      raise ValueError(
          'source_column must be a column generated with numeric_column(). '
          'Given: {}'.format(source_column))
    if len(source_column.shape) > 1:
      raise ValueError(
          'source_column must be one-dimensional column. '
          'Given: {}'.format(source_column))
    if (not boundaries or
        not (isinstance(boundaries, list) or isinstance(boundaries, tuple))):
      raise ValueError('boundaries must be a sorted list.')
    for i in range(len(boundaries) - 1):
      if boundaries[i] >= boundaries[i + 1]:
        raise ValueError('boundaries must be a sorted list.')
    return _BucketizedColumn(source_column, tuple(boundaries))
  
  
  def _assert_string_or_int(dtype, prefix):
    if (dtype != dtypes.string) and (not dtype.is_integer):
      raise ValueError(
          '{} dtype must be string or integer. dtype: {}.'.format(prefix, dtype))
  
  
  @tf_export('feature_column.categorical_column_with_hash_bucket')
  def categorical_column_with_hash_bucket(key,
                                          hash_bucket_size,
                                          dtype=dtypes.string):
    """Represents sparse feature where ids are set by hashing.
  
    Use this when your sparse features are in string or integer format, and you
    want to distribute your inputs into a finite number of buckets by hashing.
    output_id = Hash(input_feature_string) % bucket_size
  
    For input dictionary `features`, `features[key]` is either `Tensor` or
    `SparseTensor`. If `Tensor`, missing values can be represented by `-1` for int
    and `''` for string. Note that these values are independent of the
    `default_value` argument.
  
    Example:
  
    ```python
    keywords = categorical_column_with_hash_bucket("keywords", 10K)
    columns = [keywords, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
  
    # or
    keywords_embedded = embedding_column(keywords, 16)
    columns = [keywords_embedded, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
    ```
  
    Args:
      key: A unique string identifying the input feature. It is used as the
        column name and the dictionary key for feature parsing configs, feature
        `Tensor` objects, and feature columns.
      hash_bucket_size: An int > 1. The number of buckets.
      dtype: The type of features. Only string and integer types are supported.
  
    Returns:
      A `_HashedCategoricalColumn`.
  
    Raises:
      ValueError: `hash_bucket_size` is not greater than 1.
      ValueError: `dtype` is neither string nor integer.
    """
    if hash_bucket_size is None:
      raise ValueError('hash_bucket_size must be set. ' 'key: {}'.format(key))
  
    if hash_bucket_size < 1:
      raise ValueError('hash_bucket_size must be at least 1. '
                       'hash_bucket_size: {}, key: {}'.format(
                           hash_bucket_size, key))
  
    _assert_string_or_int(dtype, prefix='column_name: {}'.format(key))
  
    return _HashedCategoricalColumn(key, hash_bucket_size, dtype)
  
  
  @tf_export('feature_column.categorical_column_with_vocabulary_file')
  def categorical_column_with_vocabulary_file(key,
                                              vocabulary_file,
                                              vocabulary_size=None,
                                              num_oov_buckets=0,
                                              default_value=None,
                                              dtype=dtypes.string):
    """A `_CategoricalColumn` with a vocabulary file.
  
    Use this when your inputs are in string or integer format, and you have a
    vocabulary file that maps each value to an integer ID. By default,
    out-of-vocabulary values are ignored. Use either (but not both) of
    `num_oov_buckets` and `default_value` to specify how to include
    out-of-vocabulary values.
  
    For input dictionary `features`, `features[key]` is either `Tensor` or
    `SparseTensor`. If `Tensor`, missing values can be represented by `-1` for int
    and `''` for string. Note that these values are independent of the
    `default_value` argument.
  
    Example with `num_oov_buckets`:
    File '/us/states.txt' contains 50 lines, each with a 2-character U.S. state
    abbreviation. All inputs with values in that file are assigned an ID 0-49,
    corresponding to its line number. All other values are hashed and assigned an
    ID 50-54.
  
    ```python
    states = categorical_column_with_vocabulary_file(
        key='states', vocabulary_file='/us/states.txt', vocabulary_size=50,
        num_oov_buckets=5)
    columns = [states, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
    ```
  
    Example with `default_value`:
    File '/us/states.txt' contains 51 lines - the first line is 'XX', and the
    other 50 each have a 2-character U.S. state abbreviation. Both a literal 'XX'
    in input, and other values missing from the file, will be assigned ID 0. All
    others are assigned the corresponding line number 1-50.
  
    ```python
    states = categorical_column_with_vocabulary_file(
        key='states', vocabulary_file='/us/states.txt', vocabulary_size=51,
        default_value=0)
    columns = [states, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction, _, _ = linear_model(features, columns)
    ```
  
    And to make an embedding with either:
  
    ```python
    columns = [embedding_column(states, 3),...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
    ```
  
    Args:
      key: A unique string identifying the input feature. It is used as the
        column name and the dictionary key for feature parsing configs, feature
        `Tensor` objects, and feature columns.
      vocabulary_file: The vocabulary file name.
      vocabulary_size: Number of the elements in the vocabulary. This must be no
        greater than length of `vocabulary_file`, if less than length, later
        values are ignored. If None, it is set to the length of `vocabulary_file`.
      num_oov_buckets: Non-negative integer, the number of out-of-vocabulary
        buckets. All out-of-vocabulary inputs will be assigned IDs in the range
        `[vocabulary_size, vocabulary_size+num_oov_buckets)` based on a hash of
        the input value. A positive `num_oov_buckets` can not be specified with
        `default_value`.
      default_value: The integer ID value to return for out-of-vocabulary feature
        values, defaults to `-1`. This can not be specified with a positive
        `num_oov_buckets`.
      dtype: The type of features. Only string and integer types are supported.
  
    Returns:
      A `_CategoricalColumn` with a vocabulary file.
  
    Raises:
      ValueError: `vocabulary_file` is missing or cannot be opened.
      ValueError: `vocabulary_size` is missing or < 1.
      ValueError: `num_oov_buckets` is a negative integer.
      ValueError: `num_oov_buckets` and `default_value` are both specified.
      ValueError: `dtype` is neither string nor integer.
    """
    if not vocabulary_file:
      raise ValueError('Missing vocabulary_file in {}.'.format(key))
  
    if vocabulary_size is None:
      if not gfile.Exists(vocabulary_file):
        raise ValueError('vocabulary_file in {} does not exist.'.format(key))
  
      with gfile.GFile(vocabulary_file) as f:
        vocabulary_size = sum(1 for _ in f)
      logging.info(
          'vocabulary_size = %d in %s is inferred from the number of elements '
          'in the vocabulary_file %s.', vocabulary_size, key, vocabulary_file)
  
    # `vocabulary_size` isn't required for lookup, but it is for `_num_buckets`.
    if vocabulary_size < 1:
      raise ValueError('Invalid vocabulary_size in {}.'.format(key))
    if num_oov_buckets:
      if default_value is not None:
        raise ValueError(
            'Can\'t specify both num_oov_buckets and default_value in {}.'.format(
                key))
      if num_oov_buckets < 0:
        raise ValueError('Invalid num_oov_buckets {} in {}.'.format(
            num_oov_buckets, key))
    _assert_string_or_int(dtype, prefix='column_name: {}'.format(key))
    return _VocabularyFileCategoricalColumn(
        key=key,
        vocabulary_file=vocabulary_file,
        vocabulary_size=vocabulary_size,
        num_oov_buckets=0 if num_oov_buckets is None else num_oov_buckets,
        default_value=-1 if default_value is None else default_value,
        dtype=dtype)
  
  
  @tf_export('feature_column.categorical_column_with_vocabulary_list')
  def categorical_column_with_vocabulary_list(
      key, vocabulary_list, dtype=None, default_value=-1, num_oov_buckets=0):
    """A `_CategoricalColumn` with in-memory vocabulary.
  
    Use this when your inputs are in string or integer format, and you have an
    in-memory vocabulary mapping each value to an integer ID. By default,
    out-of-vocabulary values are ignored. Use either (but not both) of
    `num_oov_buckets` and `default_value` to specify how to include
    out-of-vocabulary values.
  
    For input dictionary `features`, `features[key]` is either `Tensor` or
    `SparseTensor`. If `Tensor`, missing values can be represented by `-1` for int
    and `''` for string. Note that these values are independent of the
    `default_value` argument.
  
    Example with `num_oov_buckets`:
    In the following example, each input in `vocabulary_list` is assigned an ID
    0-3 corresponding to its index (e.g., input 'B' produces output 2). All other
    inputs are hashed and assigned an ID 4-5.
  
    ```python
    colors = categorical_column_with_vocabulary_list(
        key='colors', vocabulary_list=('R', 'G', 'B', 'Y'),
        num_oov_buckets=2)
    columns = [colors, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction, _, _ = linear_model(features, columns)
    ```
  
    Example with `default_value`:
    In the following example, each input in `vocabulary_list` is assigned an ID
    0-4 corresponding to its index (e.g., input 'B' produces output 3). All other
    inputs are assigned `default_value` 0.
  
  
    ```python
    colors = categorical_column_with_vocabulary_list(
        key='colors', vocabulary_list=('X', 'R', 'G', 'B', 'Y'), default_value=0)
    columns = [colors, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction, _, _ = linear_model(features, columns)
    ```
  
    And to make an embedding with either:
  
    ```python
    columns = [embedding_column(colors, 3),...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
    ```
  
    Args:
      key: A unique string identifying the input feature. It is used as the
        column name and the dictionary key for feature parsing configs, feature
        `Tensor` objects, and feature columns.
      vocabulary_list: An ordered iterable defining the vocabulary. Each feature
        is mapped to the index of its value (if present) in `vocabulary_list`.
        Must be castable to `dtype`.
      dtype: The type of features. Only string and integer types are supported.
        If `None`, it will be inferred from `vocabulary_list`.
      default_value: The integer ID value to return for out-of-vocabulary feature
        values, defaults to `-1`. This can not be specified with a positive
        `num_oov_buckets`.
      num_oov_buckets: Non-negative integer, the number of out-of-vocabulary
        buckets. All out-of-vocabulary inputs will be assigned IDs in the range
        `[len(vocabulary_list), len(vocabulary_list)+num_oov_buckets)` based on a
        hash of the input value. A positive `num_oov_buckets` can not be specified
        with `default_value`.
  
    Returns:
      A `_CategoricalColumn` with in-memory vocabulary.
  
    Raises:
      ValueError: if `vocabulary_list` is empty, or contains duplicate keys.
      ValueError: `num_oov_buckets` is a negative integer.
      ValueError: `num_oov_buckets` and `default_value` are both specified.
      ValueError: if `dtype` is not integer or string.
    """
    if (vocabulary_list is None) or (len(vocabulary_list) < 1):
      raise ValueError(
          'vocabulary_list {} must be non-empty, column_name: {}'.format(
              vocabulary_list, key))
    if len(set(vocabulary_list)) != len(vocabulary_list):
      raise ValueError(
          'Duplicate keys in vocabulary_list {}, column_name: {}'.format(
              vocabulary_list, key))
    vocabulary_dtype = dtypes.as_dtype(np.array(vocabulary_list).dtype)
    if num_oov_buckets:
      if default_value != -1:
        raise ValueError(
            'Can\'t specify both num_oov_buckets and default_value in {}.'.format(
                key))
      if num_oov_buckets < 0:
        raise ValueError('Invalid num_oov_buckets {} in {}.'.format(
            num_oov_buckets, key))
    _assert_string_or_int(
        vocabulary_dtype, prefix='column_name: {} vocabulary'.format(key))
    if dtype is None:
      dtype = vocabulary_dtype
    elif dtype.is_integer != vocabulary_dtype.is_integer:
      raise ValueError(
          'dtype {} and vocabulary dtype {} do not match, column_name: {}'.format(
              dtype, vocabulary_dtype, key))
    _assert_string_or_int(dtype, prefix='column_name: {}'.format(key))
  
    return _VocabularyListCategoricalColumn(
        key=key, vocabulary_list=tuple(vocabulary_list), dtype=dtype,
        default_value=default_value, num_oov_buckets=num_oov_buckets)
  
  
  @tf_export('feature_column.categorical_column_with_identity')
  def categorical_column_with_identity(key, num_buckets, default_value=None):
    """A `_CategoricalColumn` that returns identity values.
  
    Use this when your inputs are integers in the range `[0, num_buckets)`, and
    you want to use the input value itself as the categorical ID. Values outside
    this range will result in `default_value` if specified, otherwise it will
    fail.
  
    Typically, this is used for contiguous ranges of integer indexes, but
    it doesn't have to be. This might be inefficient, however, if many of IDs
    are unused. Consider `categorical_column_with_hash_bucket` in that case.
  
    For input dictionary `features`, `features[key]` is either `Tensor` or
    `SparseTensor`. If `Tensor`, missing values can be represented by `-1` for int
    and `''` for string. Note that these values are independent of the
    `default_value` argument.
  
    In the following examples, each input in the range `[0, 1000000)` is assigned
    the same value. All other inputs are assigned `default_value` 0. Note that a
    literal 0 in inputs will result in the same default ID.
  
    Linear model:
  
    ```python
    video_id = categorical_column_with_identity(
        key='video_id', num_buckets=1000000, default_value=0)
    columns = [video_id, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction, _, _ = linear_model(features, columns)
    ```
  
    Embedding for a DNN model:
  
    ```python
    columns = [embedding_column(video_id, 9),...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
    ```
  
    Args:
      key: A unique string identifying the input feature. It is used as the
        column name and the dictionary key for feature parsing configs, feature
        `Tensor` objects, and feature columns.
      num_buckets: Range of inputs and outputs is `[0, num_buckets)`.
      default_value: If `None`, this column's graph operations will fail for
        out-of-range inputs. Otherwise, this value must be in the range
        `[0, num_buckets)`, and will replace inputs in that range.
  
    Returns:
      A `_CategoricalColumn` that returns identity values.
  
    Raises:
      ValueError: if `num_buckets` is less than one.
      ValueError: if `default_value` is not in range `[0, num_buckets)`.
    """
    if num_buckets < 1:
      raise ValueError(
          'num_buckets {} < 1, column_name {}'.format(num_buckets, key))
    if (default_value is not None) and (
        (default_value < 0) or (default_value >= num_buckets)):
      raise ValueError(
          'default_value {} not in range [0, {}), column_name {}'.format(
              default_value, num_buckets, key))
    return _IdentityCategoricalColumn(
        key=key, num_buckets=num_buckets, default_value=default_value)
  
  
  @tf_export('feature_column.indicator_column')
  def indicator_column(categorical_column):
    """Represents multi-hot representation of given categorical column.
  
    Used to wrap any `categorical_column_*` (e.g., to feed to DNN). Use
    `embedding_column` if the inputs are sparse.
  
    ```python
    name = indicator_column(categorical_column_with_vocabulary_list(
        'name', ['bob', 'george', 'wanda'])
    columns = [name, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    dense_tensor = input_layer(features, columns)
  
    dense_tensor == [[1, 0, 0]]  # If "name" bytes_list is ["bob"]
    dense_tensor == [[1, 0, 1]]  # If "name" bytes_list is ["bob", "wanda"]
    dense_tensor == [[2, 0, 0]]  # If "name" bytes_list is ["bob", "bob"]
    ```
  
    Args:
      categorical_column: A `_CategoricalColumn` which is created by
        `categorical_column_with_*` or `crossed_column` functions.
  
    Returns:
      An `_IndicatorColumn`.
    """
    return _IndicatorColumn(categorical_column)
  
  
  @tf_export('feature_column.weighted_categorical_column')
  def weighted_categorical_column(
      categorical_column, weight_feature_key, dtype=dtypes.float32):
    """Applies weight values to a `_CategoricalColumn`.
  
    Use this when each of your sparse inputs has both an ID and a value. For
    example, if you're representing text documents as a collection of word
    frequencies, you can provide 2 parallel sparse input features ('terms' and
    'frequencies' below).
  
    Example:
  
    Input `tf.Example` objects:
  
    ```proto
    [
      features {
        feature {
          key: "terms"
          value {bytes_list {value: "very" value: "model"}}
        }
        feature {
          key: "frequencies"
          value {float_list {value: 0.3 value: 0.1}}
        }
      },
      features {
        feature {
          key: "terms"
          value {bytes_list {value: "when" value: "course" value: "human"}}
        }
        feature {
          key: "frequencies"
          value {float_list {value: 0.4 value: 0.1 value: 0.2}}
        }
      }
    ]
    ```
  
    ```python
    categorical_column = categorical_column_with_hash_bucket(
        column_name='terms', hash_bucket_size=1000)
    weighted_column = weighted_categorical_column(
        categorical_column=categorical_column, weight_feature_key='frequencies')
    columns = [weighted_column, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction, _, _ = linear_model(features, columns)
    ```
  
    This assumes the input dictionary contains a `SparseTensor` for key
    'terms', and a `SparseTensor` for key 'frequencies'. These 2 tensors must have
    the same indices and dense shape.
  
    Args:
      categorical_column: A `_CategoricalColumn` created by
        `categorical_column_with_*` functions.
      weight_feature_key: String key for weight values.
      dtype: Type of weights, such as `tf.float32`. Only float and integer weights
        are supported.
  
    Returns:
      A `_CategoricalColumn` composed of two sparse features: one represents id,
      the other represents weight (value) of the id feature in that example.
  
    Raises:
      ValueError: if `dtype` is not convertible to float.
    """
    if (dtype is None) or not (dtype.is_integer or dtype.is_floating):
      raise ValueError('dtype {} is not convertible to float.'.format(dtype))
    return _WeightedCategoricalColumn(
        categorical_column=categorical_column,
        weight_feature_key=weight_feature_key,
        dtype=dtype)
  
  
  @tf_export('feature_column.crossed_column')
  def crossed_column(keys, hash_bucket_size, hash_key=None):
    """Returns a column for performing crosses of categorical features.
  
    Crossed features will be hashed according to `hash_bucket_size`. Conceptually,
    the transformation can be thought of as:
      Hash(cartesian product of features) % `hash_bucket_size`
  
    For example, if the input features are:
  
    * SparseTensor referred by first key:
  
      ```python
      shape = [2, 2]
      {
          [0, 0]: "a"
          [1, 0]: "b"
          [1, 1]: "c"
      }
      ```
  
    * SparseTensor referred by second key:
  
      ```python
      shape = [2, 1]
      {
          [0, 0]: "d"
          [1, 0]: "e"
      }
      ```
  
    then crossed feature will look like:
  
    ```python
     shape = [2, 2]
    {
        [0, 0]: Hash64("d", Hash64("a")) % hash_bucket_size
        [1, 0]: Hash64("e", Hash64("b")) % hash_bucket_size
        [1, 1]: Hash64("e", Hash64("c")) % hash_bucket_size
    }
    ```
  
    Here is an example to create a linear model with crosses of string features:
  
    ```python
    keywords_x_doc_terms = crossed_column(['keywords', 'doc_terms'], 50K)
    columns = [keywords_x_doc_terms, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
    ```
  
    You could also use vocabulary lookup before crossing:
  
    ```python
    keywords = categorical_column_with_vocabulary_file(
        'keywords', '/path/to/vocabulary/file', vocabulary_size=1K)
    keywords_x_doc_terms = crossed_column([keywords, 'doc_terms'], 50K)
    columns = [keywords_x_doc_terms, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
    ```
  
    If an input feature is of numeric type, you can use
    `categorical_column_with_identity`, or `bucketized_column`, as in the example:
  
    ```python
    # vertical_id is an integer categorical feature.
    vertical_id = categorical_column_with_identity('vertical_id', 10K)
    price = numeric_column('price')
    # bucketized_column converts numerical feature to a categorical one.
    bucketized_price = bucketized_column(price, boundaries=[...])
    vertical_id_x_price = crossed_column([vertical_id, bucketized_price], 50K)
    columns = [vertical_id_x_price, ...]
    features = tf.parse_example(..., features=make_parse_example_spec(columns))
    linear_prediction = linear_model(features, columns)
    ```
  
    To use crossed column in DNN model, you need to add it in an embedding column
    as in this example:
  
    ```python
    vertical_id_x_price = crossed_column([vertical_id, bucketized_price], 50K)
    vertical_id_x_price_embedded = embedding_column(vertical_id_x_price, 10)
    dense_tensor = input_layer(features, [vertical_id_x_price_embedded, ...])
    ```
  
    Args:
      keys: An iterable identifying the features to be crossed. Each element can
        be either:
        * string: Will use the corresponding feature which must be of string type.
        * `_CategoricalColumn`: Will use the transformed tensor produced by this
          column. Does not support hashed categorical column.
      hash_bucket_size: An int > 1. The number of buckets.
      hash_key: Specify the hash_key that will be used by the `FingerprintCat64`
        function to combine the crosses fingerprints on SparseCrossOp (optional).
  
    Returns:
      A `_CrossedColumn`.
  
    Raises:
      ValueError: If `len(keys) < 2`.
      ValueError: If any of the keys is neither a string nor `_CategoricalColumn`.
      ValueError: If any of the keys is `_HashedCategoricalColumn`.
      ValueError: If `hash_bucket_size < 1`.
    """
    if not hash_bucket_size or hash_bucket_size < 1:
      raise ValueError('hash_bucket_size must be > 1. '
                       'hash_bucket_size: {}'.format(hash_bucket_size))
    if not keys or len(keys) < 2:
      raise ValueError(
          'keys must be a list with length > 1. Given: {}'.format(keys))
    for key in keys:
      if (not isinstance(key, six.string_types) and
          not isinstance(key, _CategoricalColumn)):
        raise ValueError(
            'Unsupported key type. All keys must be either string, or '
            'categorical column except _HashedCategoricalColumn. '
            'Given: {}'.format(key))
      if isinstance(key, _HashedCategoricalColumn):
        raise ValueError(
            'categorical_column_with_hash_bucket is not supported for crossing. '
            'Hashing before crossing will increase probability of collision. '
            'Instead, use the feature name as a string. Given: {}'.format(key))
    return _CrossedColumn(
        keys=tuple(keys), hash_bucket_size=hash_bucket_size,
        hash_key=hash_key)
  
  
  # TODO(rohanj): Clearly define semantics of this layer.
  class _EmbeddingColumnLayer(base.Layer):
    """A layer that stores all the state required for a embedding column."""
  
    def __init__(self,
                 embedding_shape,
                 initializer,
                 weight_collections=None,
                 trainable=True,
                 name=None,
                 **kwargs):
      """Constructor.
  
      Args:
        embedding_shape: Shape of the embedding variable used for lookup.
        initializer: A variable initializer function to be used in embedding
          variable initialization. If not specified, defaults to
          `tf.truncated_normal_initializer` with mean `0.0` and standard deviation
          `1/sqrt(dimension)`.
        weight_collections: A list of collection names to which the Variable will
          be added. Note that, variables will also be added to collections
          `tf.GraphKeys.GLOBAL_VARIABLES` and `ops.GraphKeys.MODEL_VARIABLES`.
        trainable: If `True` also add the variable to the graph collection
          `GraphKeys.TRAINABLE_VARIABLES` (see `tf.Variable`).
        name: Name of the layer
        **kwargs: keyword named properties.
      """
      super(_EmbeddingColumnLayer, self).__init__(
          trainable=trainable, name=name, **kwargs)
      self._embedding_shape = embedding_shape
      self._initializer = initializer
      self._weight_collections = weight_collections
  
    def build(self, _):
      self._embedding_weight_var = self.add_variable(
          name='embedding_weights',
          shape=self._embedding_shape,
          dtype=dtypes.float32,
          initializer=self._initializer,
          trainable=self.trainable)
      # self.add_variable already appends to GLOBAL_VARIABLES collection.
      if self._weight_collections and not context.executing_eagerly():
        for weight_collection in self._weight_collections:
          if weight_collection != ops.GraphKeys.GLOBAL_VARIABLES:
            _add_to_collections(self._embedding_weight_var, [weight_collection])
      self.built = True
  
    def call(self, _):
      return self._embedding_weight_var
  
  
  class _FeatureColumn(object):
    """Represents a feature column abstraction.
  
    WARNING: Do not subclass this layer unless you know what you are doing:
    the API is subject to future changes.
  
    To distinguish the concept of a feature family and a specific binary feature
    within a family, we refer to a feature family like "country" as a feature
    column. Following is an example feature in a `tf.Example` format:
      {key: "country",  value: [ "US" ]}
    In this example the value of feature is "US" and "country" refers to the
    column of the feature.
  
    This class is an abstract class. User should not create instances of this.
    """
    __metaclass__ = abc.ABCMeta
  
    @abc.abstractproperty
    def name(self):
      """Returns string. Used for naming and for name_scope."""
      pass
  
    @property
    def _var_scope_name(self):
      """Returns string. Used for variable_scope. Defaults to self.name."""
      return self.name
  
    @abc.abstractmethod
    def _transform_feature(self, inputs):
      """Returns intermediate representation (usually a `Tensor`).
  
      Uses `inputs` to create an intermediate representation (usually a `Tensor`)
      that other feature columns can use.
  
      Example usage of `inputs`:
      Let's say a Feature column depends on raw feature ('raw') and another
      `_FeatureColumn` (input_fc). To access corresponding `Tensor`s, inputs will
      be used as follows:
  
      ```python
      raw_tensor = inputs.get('raw')
      fc_tensor = inputs.get(input_fc)
      ```
  
      Args:
        inputs: A `_LazyBuilder` object to access inputs.
  
      Returns:
        Transformed feature `Tensor`.
      """
      pass
  
    @abc.abstractproperty
    def _parse_example_spec(self):
      """Returns a `tf.Example` parsing spec as dict.
  
      It is used for get_parsing_spec for `tf.parse_example`. Returned spec is a
      dict from keys ('string') to `VarLenFeature`, `FixedLenFeature`, and other
      supported objects. Please check documentation of @{tf.parse_example} for all
      supported spec objects.
  
      Let's say a Feature column depends on raw feature ('raw') and another
      `_FeatureColumn` (input_fc). One possible implementation of
      _parse_example_spec is as follows:
  
      ```python
      spec = {'raw': tf.FixedLenFeature(...)}
      spec.update(input_fc._parse_example_spec)
      return spec
      ```
      """
      pass
  
    def _reset_config(self):
      """Resets the configuration in the column.
  
      Some feature columns e.g. embedding or shared embedding columns might
      have some state that is needed to be reset sometimes. Use this method
      in that scenario.
      """
  
  
  class _DenseColumn(_FeatureColumn):
    """Represents a column which can be represented as `Tensor`.
  
    WARNING: Do not subclass this layer unless you know what you are doing:
    the API is subject to future changes.
  
    Some examples of this type are: numeric_column, embedding_column,
    indicator_column.
    """
  
    __metaclass__ = abc.ABCMeta
  
    @abc.abstractproperty
    def _variable_shape(self):
      """`TensorShape` of `_get_dense_tensor`, without batch dimension."""
      pass
  
    @abc.abstractmethod
    def _get_dense_tensor(self, inputs, weight_collections=None, trainable=None):
      """Returns a `Tensor`.
  
      The output of this function will be used by model-builder-functions. For
      example the pseudo code of `input_layer` will be like:
  
      ```python
      def input_layer(features, feature_columns, ...):
        outputs = [fc._get_dense_tensor(...) for fc in feature_columns]
        return tf.concat(outputs)
      ```
  
      Args:
        inputs: A `_LazyBuilder` object to access inputs.
        weight_collections: List of graph collections to which Variables (if any
          will be created) are added.
        trainable: If `True` also add variables to the graph collection
          `GraphKeys.TRAINABLE_VARIABLES` (see @{tf.Variable}).
  
      Returns:
        `Tensor` of shape [batch_size] + `_variable_shape`.
      """
      pass
  
  
  def _create_weighted_sum(column,
                           builder,
                           units,
                           sparse_combiner,
                           weight_collections,
                           trainable,
                           weight_var=None):
    """Creates a weighted sum for a dense or sparse column for linear_model."""
    if isinstance(column, _CategoricalColumn):
      return _create_categorical_column_weighted_sum(
          column=column,
          builder=builder,
          units=units,
          sparse_combiner=sparse_combiner,
          weight_collections=weight_collections,
          trainable=trainable,
          weight_var=weight_var)
    else:
      return _create_dense_column_weighted_sum(
          column=column,
          builder=builder,
          units=units,
          weight_collections=weight_collections,
          trainable=trainable,
          weight_var=weight_var)
  
  
  def _create_dense_column_weighted_sum(column,
                                        builder,
                                        units,
                                        weight_collections,
                                        trainable,
                                        weight_var=None):
    """Create a weighted sum of a dense column for linear_model."""
    tensor = column._get_dense_tensor(  # pylint: disable=protected-access
        builder,
        weight_collections=weight_collections,
        trainable=trainable)
    num_elements = column._variable_shape.num_elements()  # pylint: disable=protected-access
    batch_size = array_ops.shape(tensor)[0]
    tensor = array_ops.reshape(tensor, shape=(batch_size, num_elements))
    if weight_var is not None:
      weight = weight_var
    else:
      weight = variable_scope.get_variable(
          name='weights',
          shape=[num_elements, units],
          initializer=init_ops.zeros_initializer(),
          trainable=trainable,
          collections=weight_collections)
    return math_ops.matmul(tensor, weight, name='weighted_sum')
  
  
  class _CategoricalColumn(_FeatureColumn):
    """Represents a categorical feature.
  
    WARNING: Do not subclass this layer unless you know what you are doing:
    the API is subject to future changes.
  
    A categorical feature typically handled with a @{tf.SparseTensor} of IDs.
    """
    __metaclass__ = abc.ABCMeta
  
    IdWeightPair = collections.namedtuple(  # pylint: disable=invalid-name
        'IdWeightPair', ['id_tensor', 'weight_tensor'])
  
    @abc.abstractproperty
    def _num_buckets(self):
      """Returns number of buckets in this sparse feature."""
      pass
  
    @abc.abstractmethod
    def _get_sparse_tensors(self,
                            inputs,
                            weight_collections=None,
                            trainable=None):
      """Returns an IdWeightPair.
  
      `IdWeightPair` is a pair of `SparseTensor`s which represents ids and
      weights.
  
      `IdWeightPair.id_tensor` is typically a `batch_size` x `num_buckets`
      `SparseTensor` of `int64`. `IdWeightPair.weight_tensor` is either a
      `SparseTensor` of `float` or `None` to indicate all weights should be
      taken to be 1. If specified, `weight_tensor` must have exactly the same
      shape and indices as `sp_ids`. Expected `SparseTensor` is same as parsing
      output of a `VarLenFeature` which is a ragged matrix.
  
      Args:
        inputs: A `LazyBuilder` as a cache to get input tensors required to
          create `IdWeightPair`.
        weight_collections: List of graph collections to which variables (if any
          will be created) are added.
        trainable: If `True` also add variables to the graph collection
          `GraphKeys.TRAINABLE_VARIABLES` (see @{tf.get_variable}).
      """
      pass
  
  
  def _create_categorical_column_weighted_sum(column,
                                              builder,
                                              units,
                                              sparse_combiner,
                                              weight_collections,
                                              trainable,
                                              weight_var=None):
    """Create a weighted sum of a categorical column for linear_model."""
    sparse_tensors = column._get_sparse_tensors(  # pylint: disable=protected-access
        builder,
        weight_collections=weight_collections,
        trainable=trainable)
    id_tensor = sparse_ops.sparse_reshape(sparse_tensors.id_tensor, [
        array_ops.shape(sparse_tensors.id_tensor)[0], -1
    ])
    weight_tensor = sparse_tensors.weight_tensor
    if weight_tensor is not None:
      weight_tensor = sparse_ops.sparse_reshape(
          weight_tensor, [array_ops.shape(weight_tensor)[0], -1])
  
    if weight_var is not None:
      weight = weight_var
    else:
      weight = variable_scope.get_variable(
          name='weights',
          shape=(column._num_buckets, units),  # pylint: disable=protected-access
          initializer=init_ops.zeros_initializer(),
          trainable=trainable,
          collections=weight_collections)
    return _safe_embedding_lookup_sparse(
        weight,
        id_tensor,
        sparse_weights=weight_tensor,
        combiner=sparse_combiner,
        name='weighted_sum')
  
  
  class _SequenceDenseColumn(_FeatureColumn):
    """Represents dense sequence data."""
  
    __metaclass__ = abc.ABCMeta
  
    TensorSequenceLengthPair = collections.namedtuple(  # pylint: disable=invalid-name
        'TensorSequenceLengthPair', ['dense_tensor', 'sequence_length'])
  
    @abc.abstractmethod
    def _get_sequence_dense_tensor(
        self, inputs, weight_collections=None, trainable=None):
      """Returns a `TensorSequenceLengthPair`."""
      pass
  
  
  class _LazyBuilder(object):
    """Handles caching of transformations while building the model.
  
    `_FeatureColumn` specifies how to digest an input column to the network. Some
    feature columns require data transformations. This class caches those
    transformations.
  
    Some features may be used in more than one place. For example, one can use a
    bucketized feature by itself and a cross with it. In that case we
    should create only one bucketization op instead of creating ops for each
    feature column separately. To handle re-use of transformed columns,
    `_LazyBuilder` caches all previously transformed columns.
  
    Example:
    We're trying to use the following `_FeatureColumn`s:
  
    ```python
    bucketized_age = fc.bucketized_column(fc.numeric_column("age"), ...)
    keywords = fc.categorical_column_with_hash_buckets("keywords", ...)
    age_X_keywords = fc.crossed_column([bucketized_age, "keywords"])
    ... = linear_model(features,
                            [bucketized_age, keywords, age_X_keywords]
    ```
  
    If we transform each column independently, then we'll get duplication of
    bucketization (one for cross, one for bucketization itself).
    The `_LazyBuilder` eliminates this duplication.
    """
  
    def __init__(self, features):
      """Creates a `_LazyBuilder`.
  
      Args:
        features: A mapping from feature column to objects that are `Tensor` or
          `SparseTensor`, or can be converted to same via
          `sparse_tensor.convert_to_tensor_or_sparse_tensor`. A `string` key
          signifies a base feature (not-transformed). A `_FeatureColumn` key
          means that this `Tensor` is the output of an existing `_FeatureColumn`
          which can be reused.
      """
      self._features = features.copy()
      self._feature_tensors = {}
  
    def get(self, key):
      """Returns a `Tensor` for the given key.
  
      A `str` key is used to access a base feature (not-transformed). When a
      `_FeatureColumn` is passed, the transformed feature is returned if it
      already exists, otherwise the given `_FeatureColumn` is asked to provide its
      transformed output, which is then cached.
  
      Args:
        key: a `str` or a `_FeatureColumn`.
  
      Returns:
        The transformed `Tensor` corresponding to the `key`.
  
      Raises:
        ValueError: if key is not found or a transformed `Tensor` cannot be
          computed.
      """
      if key in self._feature_tensors:
        # FeatureColumn is already transformed or converted.
        return self._feature_tensors[key]
  
      if key in self._features:
        feature_tensor = self._get_raw_feature_as_tensor(key)
        self._feature_tensors[key] = feature_tensor
        return feature_tensor
  
      if isinstance(key, str):
        raise ValueError('Feature {} is not in features dictionary.'.format(key))
  
      if not isinstance(key, _FeatureColumn):
        raise TypeError('"key" must be either a "str" or "_FeatureColumn". '
                        'Provided: {}'.format(key))
  
      column = key
      logging.debug('Transforming feature_column %s.', column)
      transformed = column._transform_feature(self)  # pylint: disable=protected-access
      if transformed is None:
        raise ValueError('Column {} is not supported.'.format(column.name))
      self._feature_tensors[column] = transformed
      return transformed
  
    def _get_raw_feature_as_tensor(self, key):
      """Gets the raw_feature (keyed by `key`) as `tensor`.
  
      The raw feature is converted to (sparse) tensor and maybe expand dim.
  
      For both `Tensor` and `SparseTensor`, the rank will be expanded (to 2) if
      the rank is 1. This supports dynamic rank also. For rank 0 raw feature, will
      error out as it is not supported.
  
      Args:
        key: A `str` key to access the raw feature.
  
      Returns:
        A `Tensor` or `SparseTensor`.
  
      Raises:
        ValueError: if the raw feature has rank 0.
      """
      raw_feature = self._features[key]
      feature_tensor = sparse_tensor_lib.convert_to_tensor_or_sparse_tensor(
          raw_feature)
  
      def expand_dims(input_tensor):
        # Input_tensor must have rank 1.
        if isinstance(input_tensor, sparse_tensor_lib.SparseTensor):
          return sparse_ops.sparse_reshape(
              input_tensor, [array_ops.shape(input_tensor)[0], -1])
        else:
          return array_ops.expand_dims(input_tensor, -1)
  
      rank = feature_tensor.get_shape().ndims
      if rank is not None:
        if rank == 0:
          raise ValueError(
              'Feature (key: {}) cannot have rank 0. Give: {}'.format(
                  key, feature_tensor))
        return feature_tensor if rank != 1 else expand_dims(feature_tensor)
  
      # Handle dynamic rank.
      with ops.control_dependencies([
          check_ops.assert_positive(
              array_ops.rank(feature_tensor),
              message='Feature (key: {}) cannot have rank 0. Given: {}'.format(
                  key, feature_tensor))]):
        return control_flow_ops.cond(
            math_ops.equal(1, array_ops.rank(feature_tensor)),
            lambda: expand_dims(feature_tensor),
            lambda: feature_tensor)
  
  
  # TODO(ptucker): Move to third_party/tensorflow/python/ops/sparse_ops.py
  def _shape_offsets(shape):
    """Returns moving offset for each dimension given shape."""
    offsets = []
    for dim in reversed(shape):
      if offsets:
        offsets.append(dim * offsets[-1])
      else:
        offsets.append(dim)
    offsets.reverse()
    return offsets
  
  
  # TODO(ptucker): Move to third_party/tensorflow/python/ops/sparse_ops.py
  def _to_sparse_input(input_tensor, ignore_value=None):
    """Converts a `Tensor` to a `SparseTensor`, dropping ignore_value cells.
  
    If `input_tensor` is already a `SparseTensor`, just return it.
  
    Args:
      input_tensor: A string or integer `Tensor`.
      ignore_value: Entries in `dense_tensor` equal to this value will be
        absent from the resulting `SparseTensor`. If `None`, default value of
        `dense_tensor`'s dtype will be used ('' for `str`, -1 for `int`).
  
    Returns:
      A `SparseTensor` with the same shape as `input_tensor`.
  
    Raises:
      ValueError: when `input_tensor`'s rank is `None`.
    """
    input_tensor = sparse_tensor_lib.convert_to_tensor_or_sparse_tensor(
        input_tensor)
    if isinstance(input_tensor, sparse_tensor_lib.SparseTensor):
      return input_tensor
    with ops.name_scope(None, 'to_sparse_input', (input_tensor, ignore_value,)):
      if ignore_value is None:
        if input_tensor.dtype == dtypes.string:
          # Exception due to TF strings are converted to numpy objects by default.
          ignore_value = ''
        elif input_tensor.dtype.is_integer:
          ignore_value = -1  # -1 has a special meaning of missing feature
        else:
          # NOTE: `as_numpy_dtype` is a property, so with the parentheses this is
          # constructing a new numpy object of the given type, which yields the
          # default value for that type.
          ignore_value = input_tensor.dtype.as_numpy_dtype()
      ignore_value = math_ops.cast(
          ignore_value, input_tensor.dtype, name='ignore_value')
      indices = array_ops.where(
          math_ops.not_equal(input_tensor, ignore_value), name='indices')
      return sparse_tensor_lib.SparseTensor(
          indices=indices,
          values=array_ops.gather_nd(input_tensor, indices, name='values'),
          dense_shape=array_ops.shape(
              input_tensor, out_type=dtypes.int64, name='dense_shape'))
  
  
  def _clean_feature_columns(feature_columns):
    """Verifies and normalizes `feature_columns` input."""
    if isinstance(feature_columns, _FeatureColumn):
      feature_columns = [feature_columns]
  
    if isinstance(feature_columns, collections.Iterator):
      feature_columns = list(feature_columns)
  
    if isinstance(feature_columns, dict):
      raise ValueError('Expected feature_columns to be iterable, found dict.')
  
    for column in feature_columns:
      if not isinstance(column, _FeatureColumn):
        raise ValueError('Items of feature_columns must be a _FeatureColumn. '
                         'Given (type {}): {}.'.format(type(column), column))
    if not feature_columns:
      raise ValueError('feature_columns must not be empty.')
    name_to_column = dict()
    for column in feature_columns:
      if column.name in name_to_column:
        raise ValueError('Duplicate feature column name found for columns: {} '
                         'and {}. This usually means that these columns refer to '
                         'same base feature. Either one must be discarded or a '
                         'duplicated but renamed item must be inserted in '
                         'features dict.'.format(column,
                                                 name_to_column[column.name]))
      name_to_column[column.name] = column
  
    return feature_columns
  
  
  class _NumericColumn(_DenseColumn,
                       collections.namedtuple('_NumericColumn', [
                           'key', 'shape', 'default_value', 'dtype',
                           'normalizer_fn'
                       ])):
    """see `numeric_column`."""
  
    @property
    def name(self):
      return self.key
  
    @property
    def _parse_example_spec(self):
      return {
          self.key:
              parsing_ops.FixedLenFeature(self.shape, self.dtype,
                                          self.default_value)
      }
  
    def _transform_feature(self, inputs):
      input_tensor = inputs.get(self.key)
      if isinstance(input_tensor, sparse_tensor_lib.SparseTensor):
        raise ValueError(
            'The corresponding Tensor of numerical column must be a Tensor. '
            'SparseTensor is not supported. key: {}'.format(self.key))
      if self.normalizer_fn is not None:
        input_tensor = self.normalizer_fn(input_tensor)
      return math_ops.to_float(input_tensor)
  
    @property
    def _variable_shape(self):
      return tensor_shape.TensorShape(self.shape)
  
    def _get_dense_tensor(self, inputs, weight_collections=None, trainable=None):
      """Returns dense `Tensor` representing numeric feature.
  
      Args:
        inputs: A `_LazyBuilder` object to access inputs.
        weight_collections: Unused `weight_collections` since no variables are
          created in this function.
        trainable: Unused `trainable` bool since no variables are created in
          this function.
  
      Returns:
        Dense `Tensor` created within `_transform_feature`.
      """
      # Do nothing with weight_collections and trainable since no variables are
      # created in this function.
      del weight_collections
      del trainable
      # Feature has been already transformed. Return the intermediate
      # representation created by _transform_feature.
      return inputs.get(self)
  
  
  class _BucketizedColumn(_DenseColumn, _CategoricalColumn,
                          collections.namedtuple('_BucketizedColumn', [
                              'source_column', 'boundaries'])):
    """See `bucketized_column`."""
  
    @property
    def name(self):
      return '{}_bucketized'.format(self.source_column.name)
  
    @property
    def _parse_example_spec(self):
      return self.source_column._parse_example_spec  # pylint: disable=protected-access
  
    def _transform_feature(self, inputs):
      source_tensor = inputs.get(self.source_column)
      return math_ops._bucketize(  # pylint: disable=protected-access
          source_tensor,
          boundaries=self.boundaries)
  
    @property
    def _variable_shape(self):
      return tensor_shape.TensorShape(
          tuple(self.source_column.shape) + (len(self.boundaries) + 1,))
  
    def _get_dense_tensor(self, inputs, weight_collections=None, trainable=None):
      del weight_collections
      del trainable
      input_tensor = inputs.get(self)
      return array_ops.one_hot(
          indices=math_ops.to_int64(input_tensor),
          depth=len(self.boundaries) + 1,
          on_value=1.,
          off_value=0.)
  
    @property
    def _num_buckets(self):
      # By construction, source_column is always one-dimensional.
      return (len(self.boundaries) + 1) * self.source_column.shape[0]
  
    def _get_sparse_tensors(self, inputs, weight_collections=None,
                            trainable=None):
      input_tensor = inputs.get(self)
      batch_size = array_ops.shape(input_tensor)[0]
      # By construction, source_column is always one-dimensional.
      source_dimension = self.source_column.shape[0]
  
      i1 = array_ops.reshape(
          array_ops.tile(
              array_ops.expand_dims(math_ops.range(0, batch_size), 1),
              [1, source_dimension]),
          (-1,))
      i2 = array_ops.tile(math_ops.range(0, source_dimension), [batch_size])
      # Flatten the bucket indices and unique them across dimensions
      # E.g. 2nd dimension indices will range from k to 2*k-1 with k buckets
      bucket_indices = (
          array_ops.reshape(input_tensor, (-1,)) +
          (len(self.boundaries) + 1) * i2)
  
      indices = math_ops.to_int64(array_ops.transpose(array_ops.stack((i1, i2))))
      dense_shape = math_ops.to_int64(array_ops.stack(
          [batch_size, source_dimension]))
      sparse_tensor = sparse_tensor_lib.SparseTensor(
          indices=indices,
          values=bucket_indices,
          dense_shape=dense_shape)
      return _CategoricalColumn.IdWeightPair(sparse_tensor, None)
  
  
  class _EmbeddingColumn(
      _DenseColumn, _SequenceDenseColumn,
      collections.namedtuple(
          '_EmbeddingColumn',
          ('categorical_column', 'dimension', 'combiner', 'layer_creator',
           'ckpt_to_load_from', 'tensor_name_in_ckpt', 'max_norm', 'trainable'))):
    """See `embedding_column`."""
  
    @property
    def name(self):
      if not hasattr(self, '_name'):
        self._name = '{}_embedding'.format(self.categorical_column.name)
      return self._name
  
    @property
    def _parse_example_spec(self):
      return self.categorical_column._parse_example_spec  # pylint: disable=protected-access
  
    def _transform_feature(self, inputs):
      return inputs.get(self.categorical_column)
  
    @property
    def _variable_shape(self):
      if not hasattr(self, '_shape'):
        self._shape = tensor_shape.vector(self.dimension)
      return self._shape
  
    def _get_dense_tensor_internal(self,
                                   inputs,
                                   weight_collections=None,
                                   trainable=None):
      """Private method that follows the signature of _get_dense_tensor."""
      # Get sparse IDs and weights.
      sparse_tensors = self.categorical_column._get_sparse_tensors(  # pylint: disable=protected-access
          inputs, weight_collections=weight_collections, trainable=trainable)
      sparse_ids = sparse_tensors.id_tensor
      sparse_weights = sparse_tensors.weight_tensor
  
      embedding_weights = self.layer_creator(
          weight_collections=weight_collections,
          scope=variable_scope.get_variable_scope())
  
      if self.ckpt_to_load_from is not None:
        to_restore = embedding_weights
        if isinstance(to_restore, variables.PartitionedVariable):
          to_restore = to_restore._get_variable_list()  # pylint: disable=protected-access
        checkpoint_utils.init_from_checkpoint(self.ckpt_to_load_from, {
            self.tensor_name_in_ckpt: to_restore
        })
  
      # Return embedding lookup result.
      return _safe_embedding_lookup_sparse(
          embedding_weights=embedding_weights,
          sparse_ids=sparse_ids,
          sparse_weights=sparse_weights,
          combiner=self.combiner,
          name='%s_weights' % self.name,
          max_norm=self.max_norm)
  
    def _get_dense_tensor(self, inputs, weight_collections=None, trainable=None):
      if isinstance(self.categorical_column, _SequenceCategoricalColumn):
        raise ValueError(
            'In embedding_column: {}. '
            'categorical_column must not be of type _SequenceCategoricalColumn. '
            'Suggested fix A: If you wish to use input_layer, use a '
            'non-sequence categorical_column_with_*. '
            'Suggested fix B: If you wish to create sequence input, use '
            'sequence_input_layer instead of input_layer. '
            'Given (type {}): {}'.format(
                self.name, type(self.categorical_column),
                self.categorical_column))
      return self._get_dense_tensor_internal(
          inputs=inputs,
          weight_collections=weight_collections,
          trainable=trainable)
  
    def _get_sequence_dense_tensor(
        self, inputs, weight_collections=None, trainable=None):
      if not isinstance(self.categorical_column, _SequenceCategoricalColumn):
        raise ValueError(
            'In embedding_column: {}. '
            'categorical_column must be of type _SequenceCategoricalColumn '
            'to use sequence_input_layer. '
            'Suggested fix: Use one of sequence_categorical_column_with_*. '
            'Given (type {}): {}'.format(
                self.name, type(self.categorical_column),
                self.categorical_column))
      dense_tensor = self._get_dense_tensor_internal(  # pylint: disable=protected-access
          inputs=inputs,
          weight_collections=weight_collections,
          trainable=trainable)
      sparse_tensors = self.categorical_column._get_sparse_tensors(inputs)  # pylint: disable=protected-access
      sequence_length = _sequence_length_from_sparse_tensor(
          sparse_tensors.id_tensor)
      return _SequenceDenseColumn.TensorSequenceLengthPair(
          dense_tensor=dense_tensor, sequence_length=sequence_length)
  
  
  def _get_graph_for_variable(var):
    if isinstance(var, variables.PartitionedVariable):
      return list(var)[0].graph
    else:
      return var.graph
  
  
  class _SharedEmbeddingColumn(
      _DenseColumn,
      collections.namedtuple(
          '_SharedEmbeddingColumn',
          ('categorical_column', 'dimension', 'combiner', 'initializer',
           'var_scope_name', 'ckpt_to_load_from', 'tensor_name_in_ckpt',
           'max_norm', 'trainable'))):
    """See `embedding_column`."""
  
    @property
    def name(self):
      if not hasattr(self, '_name'):
        self._name = '{}_shared_embedding'.format(self.categorical_column.name)
      return self._name
  
    @property
    def _var_scope_name(self):
      return self.var_scope_name
  
    @property
    def _parse_example_spec(self):
      return self.categorical_column._parse_example_spec  # pylint: disable=protected-access
  
    def _transform_feature(self, inputs):
      return inputs.get(self.categorical_column)
  
    def _set_layer(self, layer):
      self._layer = layer
  
    def _set_all_columns(self, all_columns):
      self._all_columns = all_columns
  
    def _reset_config(self):
      config = self._layer.get_config()
      config['embedding_shape'] = (
          self.categorical_column._num_buckets,  # pylint: disable=protected-access
          self.dimension)
      config['initializer'] = self.initializer
      self._layer = self._layer.__class__.from_config(config)
      for column in self._all_columns:
        column._set_layer(self._layer)  # pylint: disable=protected-access
  
    @property
    def _variable_shape(self):
      if not hasattr(self, '_shape'):
        self._shape = tensor_shape.vector(self.dimension)
      return self._shape
  
    def _get_dense_tensor(self, inputs, weight_collections=None, trainable=None):
      # This method is called from a variable_scope with name _var_scope_name,
      # which is shared among all shared embeddings. Open a name_scope here, so
      # that the ops for different columns have distinct names.
      with ops.name_scope(None, default_name=self.name):
        # Get sparse IDs and weights.
        sparse_tensors = self.categorical_column._get_sparse_tensors(  # pylint: disable=protected-access
            inputs, weight_collections=weight_collections, trainable=trainable)
        sparse_ids = sparse_tensors.id_tensor
        sparse_weights = sparse_tensors.weight_tensor
  
        embedding_weights = self._layer(
            None, scope=variable_scope.get_variable_scope())
        # If we're in graph mode and this is called with a different graph,
        # then we should reset.
        if not context.executing_eagerly() and (
            ops.get_default_graph() !=
            _get_graph_for_variable(embedding_weights)):
          self._reset_config()
          embedding_weights = self._layer(
              None, scope=variable_scope.get_variable_scope())
  
        if self.ckpt_to_load_from is not None:
          to_restore = embedding_weights
          if isinstance(to_restore, variables.PartitionedVariable):
            to_restore = to_restore._get_variable_list()  # pylint: disable=protected-access
          checkpoint_utils.init_from_checkpoint(self.ckpt_to_load_from, {
              self.tensor_name_in_ckpt: to_restore
          })
  
        # Return embedding lookup result.
        return _safe_embedding_lookup_sparse(
            embedding_weights=embedding_weights,
            sparse_ids=sparse_ids,
            sparse_weights=sparse_weights,
            combiner=self.combiner,
            name='%s_weights' % self.name,
            max_norm=self.max_norm)
  
  
  def _create_tuple(shape, value):
    """Returns a tuple with given shape and filled with value."""
    if shape:
      return tuple([_create_tuple(shape[1:], value) for _ in range(shape[0])])
    return value
  
  
  def _as_tuple(value):
    if not nest.is_sequence(value):
      return value
    return tuple([_as_tuple(v) for v in value])
  
  
  def _check_shape(shape, key):
    """Returns shape if it's valid, raises error otherwise."""
    assert shape is not None
    if not nest.is_sequence(shape):
      shape = [shape]
    shape = tuple(shape)
    for dimension in shape:
      if not isinstance(dimension, int):
        raise TypeError('shape dimensions must be integer. '
                        'shape: {}, key: {}'.format(shape, key))
      if dimension < 1:
        raise ValueError('shape dimensions must be greater than 0. '
                         'shape: {}, key: {}'.format(shape, key))
    return shape
  
  
  def _is_shape_and_default_value_compatible(default_value, shape):
    """Verifies compatibility of shape and default_value."""
    # Invalid condition:
    #  * if default_value is not a scalar and shape is empty
    #  * or if default_value is an iterable and shape is not empty
    if nest.is_sequence(default_value) != bool(shape):
      return False
    if not shape:
      return True
    if len(default_value) != shape[0]:
      return False
    for i in range(shape[0]):
      if not _is_shape_and_default_value_compatible(default_value[i], shape[1:]):
        return False
    return True
  
  
  def _check_default_value(shape, default_value, dtype, key):
    """Returns default value as tuple if it's valid, otherwise raises errors.
  
    This function verifies that `default_value` is compatible with both `shape`
    and `dtype`. If it is not compatible, it raises an error. If it is compatible,
    it casts default_value to a tuple and returns it. `key` is used only
    for error message.
  
    Args:
      shape: An iterable of integers specifies the shape of the `Tensor`.
      default_value: If a single value is provided, the same value will be applied
        as the default value for every item. If an iterable of values is
        provided, the shape of the `default_value` should be equal to the given
        `shape`.
      dtype: defines the type of values. Default value is `tf.float32`. Must be a
        non-quantized, real integer or floating point type.
      key: Column name, used only for error messages.
  
    Returns:
      A tuple which will be used as default value.
  
    Raises:
      TypeError: if `default_value` is an iterable but not compatible with `shape`
      TypeError: if `default_value` is not compatible with `dtype`.
      ValueError: if `dtype` is not convertible to `tf.float32`.
    """
    if default_value is None:
      return None
  
    if isinstance(default_value, int):
      return _create_tuple(shape, default_value)
  
    if isinstance(default_value, float) and dtype.is_floating:
      return _create_tuple(shape, default_value)
  
    if callable(getattr(default_value, 'tolist', None)):  # Handles numpy arrays
      default_value = default_value.tolist()
  
    if nest.is_sequence(default_value):
      if not _is_shape_and_default_value_compatible(default_value, shape):
        raise ValueError(
            'The shape of default_value must be equal to given shape. '
            'default_value: {}, shape: {}, key: {}'.format(
                default_value, shape, key))
      # Check if the values in the list are all integers or are convertible to
      # floats.
      is_list_all_int = all(
          isinstance(v, int) for v in nest.flatten(default_value))
      is_list_has_float = any(
          isinstance(v, float) for v in nest.flatten(default_value))
      if is_list_all_int:
        return _as_tuple(default_value)
      if is_list_has_float and dtype.is_floating:
        return _as_tuple(default_value)
    raise TypeError('default_value must be compatible with dtype. '
                    'default_value: {}, dtype: {}, key: {}'.format(
                        default_value, dtype, key))
  
  
  class _HashedCategoricalColumn(
      _CategoricalColumn,
      collections.namedtuple('_HashedCategoricalColumn',
                             ['key', 'hash_bucket_size', 'dtype'])):
    """see `categorical_column_with_hash_bucket`."""
  
    @property
    def name(self):
      return self.key
  
    @property
    def _parse_example_spec(self):
      return {self.key: parsing_ops.VarLenFeature(self.dtype)}
  
    def _transform_feature(self, inputs):
      input_tensor = _to_sparse_input(inputs.get(self.key))
      if not isinstance(input_tensor, sparse_tensor_lib.SparseTensor):
        raise ValueError('SparseColumn input must be a SparseTensor.')
  
      _assert_string_or_int(
          input_tensor.dtype,
          prefix='column_name: {} input_tensor'.format(self.key))
  
      if self.dtype.is_integer != input_tensor.dtype.is_integer:
        raise ValueError(
            'Column dtype and SparseTensors dtype must be compatible. '
            'key: {}, column dtype: {}, tensor dtype: {}'.format(
                self.key, self.dtype, input_tensor.dtype))
  
      if self.dtype == dtypes.string:
        sparse_values = input_tensor.values
      else:
        sparse_values = string_ops.as_string(input_tensor.values)
  
      sparse_id_values = string_ops.string_to_hash_bucket_fast(
          sparse_values, self.hash_bucket_size, name='lookup')
      return sparse_tensor_lib.SparseTensor(
          input_tensor.indices, sparse_id_values, input_tensor.dense_shape)
  
    @property
    def _num_buckets(self):
      """Returns number of buckets in this sparse feature."""
      return self.hash_bucket_size
  
    def _get_sparse_tensors(self, inputs, weight_collections=None,
                            trainable=None):
      return _CategoricalColumn.IdWeightPair(inputs.get(self), None)
  
  
  class _VocabularyFileCategoricalColumn(
      _CategoricalColumn,
      collections.namedtuple('_VocabularyFileCategoricalColumn', (
          'key', 'vocabulary_file', 'vocabulary_size', 'num_oov_buckets', 'dtype',
          'default_value'
      ))):
    """See `categorical_column_with_vocabulary_file`."""
  
    @property
    def name(self):
      return self.key
  
    @property
    def _parse_example_spec(self):
      return {self.key: parsing_ops.VarLenFeature(self.dtype)}
  
    def _transform_feature(self, inputs):
      input_tensor = _to_sparse_input(inputs.get(self.key))
  
      if self.dtype.is_integer != input_tensor.dtype.is_integer:
        raise ValueError(
            'Column dtype and SparseTensors dtype must be compatible. '
            'key: {}, column dtype: {}, tensor dtype: {}'.format(
                self.key, self.dtype, input_tensor.dtype))
  
      _assert_string_or_int(
          input_tensor.dtype,
          prefix='column_name: {} input_tensor'.format(self.key))
  
      key_dtype = self.dtype
      if input_tensor.dtype.is_integer:
        # `index_table_from_file` requires 64-bit integer keys.
        key_dtype = dtypes.int64
        input_tensor = math_ops.to_int64(input_tensor)
  
      return lookup_ops.index_table_from_file(
          vocabulary_file=self.vocabulary_file,
          num_oov_buckets=self.num_oov_buckets,
          vocab_size=self.vocabulary_size,
          default_value=self.default_value,
          key_dtype=key_dtype,
          name='{}_lookup'.format(self.key)).lookup(input_tensor)
  
    @property
    def _num_buckets(self):
      """Returns number of buckets in this sparse feature."""
      return self.vocabulary_size + self.num_oov_buckets
  
    def _get_sparse_tensors(
        self, inputs, weight_collections=None, trainable=None):
      return _CategoricalColumn.IdWeightPair(inputs.get(self), None)
  
  
  class _VocabularyListCategoricalColumn(
      _CategoricalColumn,
      collections.namedtuple('_VocabularyListCategoricalColumn', (
          'key', 'vocabulary_list', 'dtype', 'default_value', 'num_oov_buckets'
      ))):
    """See `categorical_column_with_vocabulary_list`."""
  
    @property
    def name(self):
      return self.key
  
    @property
    def _parse_example_spec(self):
      return {self.key: parsing_ops.VarLenFeature(self.dtype)}
  
    def _transform_feature(self, inputs):
      input_tensor = _to_sparse_input(inputs.get(self.key))
  
      if self.dtype.is_integer != input_tensor.dtype.is_integer:
        raise ValueError(
            'Column dtype and SparseTensors dtype must be compatible. '
            'key: {}, column dtype: {}, tensor dtype: {}'.format(
                self.key, self.dtype, input_tensor.dtype))
  
      _assert_string_or_int(
          input_tensor.dtype,
          prefix='column_name: {} input_tensor'.format(self.key))
  
      key_dtype = self.dtype
      if input_tensor.dtype.is_integer:
        # `index_table_from_tensor` requires 64-bit integer keys.
        key_dtype = dtypes.int64
        input_tensor = math_ops.to_int64(input_tensor)
  
      return lookup_ops.index_table_from_tensor(
          vocabulary_list=tuple(self.vocabulary_list),
          default_value=self.default_value,
          num_oov_buckets=self.num_oov_buckets,
          dtype=key_dtype,
          name='{}_lookup'.format(self.key)).lookup(input_tensor)
  
    @property
    def _num_buckets(self):
      """Returns number of buckets in this sparse feature."""
      return len(self.vocabulary_list) + self.num_oov_buckets
  
    def _get_sparse_tensors(
        self, inputs, weight_collections=None, trainable=None):
      return _CategoricalColumn.IdWeightPair(inputs.get(self), None)
  
  
  class _IdentityCategoricalColumn(
      _CategoricalColumn,
      collections.namedtuple('_IdentityCategoricalColumn', (
          'key', 'num_buckets', 'default_value'
      ))):
  
    """See `categorical_column_with_identity`."""
  
    @property
    def name(self):
      return self.key
  
    @property
    def _parse_example_spec(self):
      return {self.key: parsing_ops.VarLenFeature(dtypes.int64)}
  
    def _transform_feature(self, inputs):
      input_tensor = _to_sparse_input(inputs.get(self.key))
  
      if not input_tensor.dtype.is_integer:
        raise ValueError(
            'Invalid input, not integer. key: {} dtype: {}'.format(
                self.key, input_tensor.dtype))
  
      values = math_ops.to_int64(input_tensor.values, name='values')
      num_buckets = math_ops.to_int64(self.num_buckets, name='num_buckets')
      zero = math_ops.to_int64(0, name='zero')
      if self.default_value is None:
        # Fail if values are out-of-range.
        assert_less = check_ops.assert_less(
            values, num_buckets, data=(values, num_buckets),
            name='assert_less_than_num_buckets')
        assert_greater = check_ops.assert_greater_equal(
            values, zero, data=(values,),
            name='assert_greater_or_equal_0')
        with ops.control_dependencies((assert_less, assert_greater)):
          values = array_ops.identity(values)
      else:
        # Assign default for out-of-range values.
        values = array_ops.where(
            math_ops.logical_or(
                values < zero, values >= num_buckets, name='out_of_range'),
            array_ops.fill(
                dims=array_ops.shape(values),
                value=math_ops.to_int64(self.default_value),
                name='default_values'),
            values)
  
      return sparse_tensor_lib.SparseTensor(
          indices=input_tensor.indices,
          values=values,
          dense_shape=input_tensor.dense_shape)
  
    @property
    def _num_buckets(self):
      """Returns number of buckets in this sparse feature."""
      return self.num_buckets
  
    def _get_sparse_tensors(
        self, inputs, weight_collections=None, trainable=None):
      return _CategoricalColumn.IdWeightPair(inputs.get(self), None)
  
  
  class _WeightedCategoricalColumn(
      _CategoricalColumn,
      collections.namedtuple('_WeightedCategoricalColumn', (
          'categorical_column', 'weight_feature_key', 'dtype'
      ))):
    """See `weighted_categorical_column`."""
  
    @property
    def name(self):
      return '{}_weighted_by_{}'.format(
          self.categorical_column.name, self.weight_feature_key)
  
    @property
    def _parse_example_spec(self):
      config = self.categorical_column._parse_example_spec  # pylint: disable=protected-access
      if self.weight_feature_key in config:
        raise ValueError('Parse config {} already exists for {}.'.format(
            config[self.weight_feature_key], self.weight_feature_key))
      config[self.weight_feature_key] = parsing_ops.VarLenFeature(self.dtype)
      return config
  
    @property
    def _num_buckets(self):
      return self.categorical_column._num_buckets  # pylint: disable=protected-access
  
    def _transform_feature(self, inputs):
      weight_tensor = inputs.get(self.weight_feature_key)
      if weight_tensor is None:
        raise ValueError('Missing weights {}.'.format(self.weight_feature_key))
      weight_tensor = sparse_tensor_lib.convert_to_tensor_or_sparse_tensor(
          weight_tensor)
      if self.dtype != weight_tensor.dtype.base_dtype:
        raise ValueError('Bad dtype, expected {}, but got {}.'.format(
            self.dtype, weight_tensor.dtype))
      if not isinstance(weight_tensor, sparse_tensor_lib.SparseTensor):
        # The weight tensor can be a regular Tensor. In this case, sparsify it.
        weight_tensor = _to_sparse_input(weight_tensor, ignore_value=0.0)
      if not weight_tensor.dtype.is_floating:
        weight_tensor = math_ops.to_float(weight_tensor)
      return (inputs.get(self.categorical_column), weight_tensor)
  
    def _get_sparse_tensors(
        self, inputs, weight_collections=None, trainable=None):
      del weight_collections
      del trainable
      tensors = inputs.get(self)
      return _CategoricalColumn.IdWeightPair(tensors[0], tensors[1])
  
  
  class _CrossedColumn(
      _CategoricalColumn,
      collections.namedtuple('_CrossedColumn',
                             ['keys', 'hash_bucket_size', 'hash_key'])):
    """See `crossed_column`."""
  
    @property
    def name(self):
      feature_names = []
      for key in _collect_leaf_level_keys(self):
        if isinstance(key, _FeatureColumn):
          feature_names.append(key.name)
        else:  # key must be a string
          feature_names.append(key)
      return '_X_'.join(sorted(feature_names))
  
    @property
    def _parse_example_spec(self):
      config = {}
      for key in self.keys:
        if isinstance(key, _FeatureColumn):
          config.update(key._parse_example_spec)  # pylint: disable=protected-access
        else:  # key must be a string
          config.update({key: parsing_ops.VarLenFeature(dtypes.string)})
      return config
  
    def _transform_feature(self, inputs):
      feature_tensors = []
      for key in _collect_leaf_level_keys(self):
        if isinstance(key, six.string_types):
          feature_tensors.append(inputs.get(key))
        elif isinstance(key, _CategoricalColumn):
          ids_and_weights = key._get_sparse_tensors(inputs)  # pylint: disable=protected-access
          if ids_and_weights.weight_tensor is not None:
            raise ValueError(
                'crossed_column does not support weight_tensor, but the given '
                'column populates weight_tensor. '
                'Given column: {}'.format(key.name))
          feature_tensors.append(ids_and_weights.id_tensor)
        else:
          raise ValueError('Unsupported column type. Given: {}'.format(key))
      return sparse_ops._sparse_cross_hashed(  # pylint: disable=protected-access
          inputs=feature_tensors,
          num_buckets=self.hash_bucket_size,
          hash_key=self.hash_key)
  
    @property
    def _num_buckets(self):
      """Returns number of buckets in this sparse feature."""
      return self.hash_bucket_size
  
    def _get_sparse_tensors(self, inputs, weight_collections=None,
                            trainable=None):
      return _CategoricalColumn.IdWeightPair(inputs.get(self), None)
  
  
  def _collect_leaf_level_keys(cross):
    """Collects base keys by expanding all nested crosses.
  
    Args:
      cross: A `_CrossedColumn`.
  
    Returns:
      A list of strings or `_CategoricalColumn` instances.
    """
    leaf_level_keys = []
    for k in cross.keys:
      if isinstance(k, _CrossedColumn):
        leaf_level_keys.extend(_collect_leaf_level_keys(k))
      else:
        leaf_level_keys.append(k)
    return leaf_level_keys
  
  
  # TODO(zakaria): Move this to embedding_ops and make it public.
  def _safe_embedding_lookup_sparse(embedding_weights,
                                    sparse_ids,
                                    sparse_weights=None,
                                    combiner='mean',
                                    default_id=None,
                                    name=None,
                                    partition_strategy='div',
                                    max_norm=None):
    """Lookup embedding results, accounting for invalid IDs and empty features.
  
    The partitioned embedding in `embedding_weights` must all be the same shape
    except for the first dimension. The first dimension is allowed to vary as the
    vocabulary size is not necessarily a multiple of `P`.  `embedding_weights`
    may be a `PartitionedVariable` as returned by using `tf.get_variable()` with a
    partitioner.
  
    Invalid IDs (< 0) are pruned from input IDs and weights, as well as any IDs
    with non-positive weight. For an entry with no features, the embedding vector
    for `default_id` is returned, or the 0-vector if `default_id` is not supplied.
  
    The ids and weights may be multi-dimensional. Embeddings are always aggregated
    along the last dimension.
  
    Args:
      embedding_weights:  A list of `P` float `Tensor`s or values representing
          partitioned embedding `Tensor`s.  Alternatively, a `PartitionedVariable`
          created by partitioning along dimension 0.  The total unpartitioned
          shape should be `[e_0, e_1, ..., e_m]`, where `e_0` represents the
          vocab size and `e_1, ..., e_m` are the embedding dimensions.
      sparse_ids: `SparseTensor` of shape `[d_0, d_1, ..., d_n]` containing the
          ids. `d_0` is typically batch size.
      sparse_weights: `SparseTensor` of same shape as `sparse_ids`, containing
          float weights corresponding to `sparse_ids`, or `None` if all weights
          are be assumed to be 1.0.
      combiner: A string specifying how to combine embedding results for each
          entry. Currently "mean", "sqrtn" and "sum" are supported, with "mean"
          the default.
      default_id: The id to use for an entry with no features.
      name: A name for this operation (optional).
      partition_strategy: A string specifying the partitioning strategy.
          Currently `"div"` and `"mod"` are supported. Default is `"div"`.
      max_norm: If not `None`, all embeddings are l2-normalized to max_norm before
          combining.
  
  
    Returns:
      Dense `Tensor` of shape `[d_0, d_1, ..., d_{n-1}, e_1, ..., e_m]`.
  
    Raises:
      ValueError: if `embedding_weights` is empty.
    """
    if embedding_weights is None:
      raise ValueError('Missing embedding_weights %s.' % embedding_weights)
    if isinstance(embedding_weights, variables.PartitionedVariable):
      embedding_weights = list(embedding_weights)  # get underlying Variables.
    if not isinstance(embedding_weights, list):
      embedding_weights = [embedding_weights]
    if len(embedding_weights) < 1:
      raise ValueError('Missing embedding_weights %s.' % embedding_weights)
  
    dtype = sparse_weights.dtype if sparse_weights is not None else None
    embedding_weights = [
        ops.convert_to_tensor(w, dtype=dtype) for w in embedding_weights
    ]
  
    with ops.name_scope(name, 'embedding_lookup',
                        embedding_weights + [sparse_ids,
                                             sparse_weights]) as scope:
      # Reshape higher-rank sparse ids and weights to linear segment ids.
      original_shape = sparse_ids.dense_shape
      original_rank_dim = sparse_ids.dense_shape.get_shape()[0]
      original_rank = (
          array_ops.size(original_shape)
          if original_rank_dim.value is None
          else original_rank_dim.value)
      sparse_ids = sparse_ops.sparse_reshape(sparse_ids, [
          math_ops.reduce_prod(
              array_ops.slice(original_shape, [0], [original_rank - 1])),
          array_ops.gather(original_shape, original_rank - 1)])
      if sparse_weights is not None:
        sparse_weights = sparse_tensor_lib.SparseTensor(
            sparse_ids.indices,
            sparse_weights.values, sparse_ids.dense_shape)
  
      # Prune invalid ids and weights.
      sparse_ids, sparse_weights = _prune_invalid_ids(sparse_ids, sparse_weights)
      if combiner != 'sum':
        sparse_ids, sparse_weights = _prune_invalid_weights(
            sparse_ids, sparse_weights)
  
      # Fill in dummy values for empty features, if necessary.
      sparse_ids, is_row_empty = sparse_ops.sparse_fill_empty_rows(sparse_ids,
                                                                   default_id or
                                                                   0)
      if sparse_weights is not None:
        sparse_weights, _ = sparse_ops.sparse_fill_empty_rows(sparse_weights, 1.0)
  
      result = embedding_ops.embedding_lookup_sparse(
          embedding_weights,
          sparse_ids,
          sparse_weights,
          combiner=combiner,
          partition_strategy=partition_strategy,
          name=None if default_id is None else scope,
          max_norm=max_norm)
  
      if default_id is None:
        # Broadcast is_row_empty to the same shape as embedding_lookup_result,
        # for use in Select.
        is_row_empty = array_ops.tile(
            array_ops.reshape(is_row_empty, [-1, 1]),
            array_ops.stack([1, array_ops.shape(result)[1]]))
  
        result = array_ops.where(is_row_empty,
                                 array_ops.zeros_like(result),
                                 result,
                                 name=scope)
  
      # Reshape back from linear ids back into higher-dimensional dense result.
      final_result = array_ops.reshape(
          result,
          array_ops.concat([
              array_ops.slice(
                  math_ops.cast(original_shape, dtypes.int32), [0],
                  [original_rank - 1]),
              array_ops.slice(array_ops.shape(result), [1], [-1])
          ], 0))
      final_result.set_shape(tensor_shape.unknown_shape(
          (original_rank_dim - 1).value).concatenate(result.get_shape()[1:]))
      return final_result
  
  
  def _prune_invalid_ids(sparse_ids, sparse_weights):
    """Prune invalid IDs (< 0) from the input ids and weights."""
    is_id_valid = math_ops.greater_equal(sparse_ids.values, 0)
    if sparse_weights is not None:
      is_id_valid = math_ops.logical_and(
          is_id_valid,
          array_ops.ones_like(sparse_weights.values, dtype=dtypes.bool))
    sparse_ids = sparse_ops.sparse_retain(sparse_ids, is_id_valid)
    if sparse_weights is not None:
      sparse_weights = sparse_ops.sparse_retain(sparse_weights, is_id_valid)
    return sparse_ids, sparse_weights
  
  
  def _prune_invalid_weights(sparse_ids, sparse_weights):
    """Prune invalid weights (< 0) from the input ids and weights."""
    if sparse_weights is not None:
      is_weights_valid = math_ops.greater(sparse_weights.values, 0)
      sparse_ids = sparse_ops.sparse_retain(sparse_ids, is_weights_valid)
      sparse_weights = sparse_ops.sparse_retain(sparse_weights, is_weights_valid)
    return sparse_ids, sparse_weights
  
  
  class _IndicatorColumn(_DenseColumn, _SequenceDenseColumn,
                         collections.namedtuple('_IndicatorColumn',
                                                ['categorical_column'])):
    """Represents a one-hot column for use in deep networks.
  
    Args:
      categorical_column: A `_CategoricalColumn` which is created by
        `categorical_column_with_*` function.
    """
  
    @property
    def name(self):
      return '{}_indicator'.format(self.categorical_column.name)
  
    def _transform_feature(self, inputs):
      """Returns dense `Tensor` representing feature.
  
      Args:
        inputs: A `_LazyBuilder` object to access inputs.
  
      Returns:
        Transformed feature `Tensor`.
  
      Raises:
        ValueError: if input rank is not known at graph building time.
      """
      id_weight_pair = self.categorical_column._get_sparse_tensors(inputs)  # pylint: disable=protected-access
      id_tensor = id_weight_pair.id_tensor
      weight_tensor = id_weight_pair.weight_tensor
  
      # If the underlying column is weighted, return the input as a dense tensor.
      if weight_tensor is not None:
        weighted_column = sparse_ops.sparse_merge(
            sp_ids=id_tensor,
            sp_values=weight_tensor,
            vocab_size=int(self._variable_shape[-1]))
        # Remove (?, -1) index
        weighted_column = sparse_ops.sparse_slice(weighted_column, [0, 0],
                                                  weighted_column.dense_shape)
        return sparse_ops.sparse_tensor_to_dense(weighted_column)
  
      dense_id_tensor = sparse_ops.sparse_tensor_to_dense(
          id_tensor, default_value=-1)
  
      # One hot must be float for tf.concat reasons since all other inputs to
      # input_layer are float32.
      one_hot_id_tensor = array_ops.one_hot(
          dense_id_tensor,
          depth=self._variable_shape[-1],
          on_value=1.0,
          off_value=0.0)
  
      # Reduce to get a multi-hot per example.
      return math_ops.reduce_sum(one_hot_id_tensor, axis=[-2])
  
    @property
    def _parse_example_spec(self):
      return self.categorical_column._parse_example_spec  # pylint: disable=protected-access
  
    @property
    def _variable_shape(self):
      """Returns a `TensorShape` representing the shape of the dense `Tensor`."""
      return tensor_shape.TensorShape([1, self.categorical_column._num_buckets])  # pylint: disable=protected-access
  
    def _get_dense_tensor(self, inputs, weight_collections=None, trainable=None):
      """Returns dense `Tensor` representing feature.
  
      Args:
        inputs: A `_LazyBuilder` object to access inputs.
        weight_collections: Unused `weight_collections` since no variables are
          created in this function.
        trainable: Unused `trainable` bool since no variables are created in
          this function.
  
      Returns:
        Dense `Tensor` created within `_transform_feature`.
  
      Raises:
        ValueError: If `categorical_column` is a `_SequenceCategoricalColumn`.
      """
      # Do nothing with weight_collections and trainable since no variables are
      # created in this function.
      del weight_collections
      del trainable
      if isinstance(self.categorical_column, _SequenceCategoricalColumn):
        raise ValueError(
            'In indicator_column: {}. '
            'categorical_column must not be of type _SequenceCategoricalColumn. '
            'Suggested fix A: If you wish to use input_layer, use a '
            'non-sequence categorical_column_with_*. '
            'Suggested fix B: If you wish to create sequence input, use '
            'sequence_input_layer instead of input_layer. '
            'Given (type {}): {}'.format(
                self.name, type(self.categorical_column),
                self.categorical_column))
      # Feature has been already transformed. Return the intermediate
      # representation created by _transform_feature.
      return inputs.get(self)
  
    def _get_sequence_dense_tensor(
        self, inputs, weight_collections=None, trainable=None):
      # Do nothing with weight_collections and trainable since no variables are
      # created in this function.
      del weight_collections
      del trainable
      if not isinstance(self.categorical_column, _SequenceCategoricalColumn):
        raise ValueError(
            'In indicator_column: {}. '
            'categorical_column must be of type _SequenceCategoricalColumn '
            'to use sequence_input_layer. '
            'Suggested fix: Use one of sequence_categorical_column_with_*. '
            'Given (type {}): {}'.format(
                self.name, type(self.categorical_column),
                self.categorical_column))
      # Feature has been already transformed. Return the intermediate
      # representation created by _transform_feature.
      dense_tensor = inputs.get(self)
      sparse_tensors = self.categorical_column._get_sparse_tensors(inputs)  # pylint: disable=protected-access
      sequence_length = _sequence_length_from_sparse_tensor(
          sparse_tensors.id_tensor)
      return _SequenceDenseColumn.TensorSequenceLengthPair(
          dense_tensor=dense_tensor, sequence_length=sequence_length)
  
  
  def _verify_static_batch_size_equality(tensors, columns):
    # bath_size is a tf.Dimension object.
    expected_batch_size = None
    for i in range(0, len(tensors)):
      if tensors[i].shape[0].value is not None:
        if expected_batch_size is None:
          bath_size_column_index = i
          expected_batch_size = tensors[i].shape[0]
        elif not expected_batch_size.is_compatible_with(tensors[i].shape[0]):
          raise ValueError(
              'Batch size (first dimension) of each feature must be same. '
              'Batch size of columns ({}, {}): ({}, {})'.format(
                  columns[bath_size_column_index].name, columns[i].name,
                  expected_batch_size, tensors[i].shape[0]))
  
  
  def _sequence_length_from_sparse_tensor(sp_tensor, num_elements=1):
    """Returns a [batch_size] Tensor with per-example sequence length."""
    with ops.name_scope(None, 'sequence_length') as name_scope:
      row_ids = sp_tensor.indices[:, 0]
      column_ids = sp_tensor.indices[:, 1]
      column_ids += array_ops.ones_like(column_ids)
      seq_length = math_ops.to_int64(
          math_ops.segment_max(column_ids, segment_ids=row_ids) / num_elements)
      # If the last n rows do not have ids, seq_length will have shape
      # [batch_size - n]. Pad the remaining values with zeros.
      n_pad = array_ops.shape(sp_tensor)[:1] - array_ops.shape(seq_length)[:1]
      padding = array_ops.zeros(n_pad, dtype=seq_length.dtype)
      return array_ops.concat([seq_length, padding], axis=0, name=name_scope)
  
  
  class _SequenceCategoricalColumn(
      _CategoricalColumn,
      collections.namedtuple(
          '_SequenceCategoricalColumn', ['categorical_column'])):
    """Represents sequences of categorical data."""
  
    @property
    def name(self):
      return self.categorical_column.name
  
    @property
    def _parse_example_spec(self):
      return self.categorical_column._parse_example_spec  # pylint: disable=protected-access
  
    def _transform_feature(self, inputs):
      return self.categorical_column._transform_feature(inputs)  # pylint: disable=protected-access
  
    @property
    def _num_buckets(self):
      return self.categorical_column._num_buckets  # pylint: disable=protected-access
  
    def _get_sparse_tensors(self, inputs, weight_collections=None,
                            trainable=None):
      sparse_tensors = self.categorical_column._get_sparse_tensors(inputs)  # pylint: disable=protected-access
      id_tensor = sparse_tensors.id_tensor
      weight_tensor = sparse_tensors.weight_tensor
      # Expands final dimension, so that embeddings are not combined during
      # embedding lookup.
      check_id_rank = check_ops.assert_equal(
          array_ops.rank(id_tensor), 2,
          data=[
              'Column {} expected ID tensor of rank 2. '.format(self.name),
              'id_tensor shape: ', array_ops.shape(id_tensor)])
      with ops.control_dependencies([check_id_rank]):
        id_tensor = sparse_ops.sparse_reshape(
            id_tensor,
            shape=array_ops.concat([id_tensor.dense_shape, [1]], axis=0))
      if weight_tensor is not None:
        check_weight_rank = check_ops.assert_equal(
            array_ops.rank(weight_tensor), 2,
            data=[
                'Column {} expected weight tensor of rank 2.'.format(self.name),
                'weight_tensor shape:', array_ops.shape(weight_tensor)])
        with ops.control_dependencies([check_weight_rank]):
          weight_tensor = sparse_ops.sparse_reshape(
              weight_tensor,
              shape=array_ops.concat([weight_tensor.dense_shape, [1]], axis=0))
      return _CategoricalColumn.IdWeightPair(id_tensor, weight_tensor)
  