text: # Copyright 2015 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.
  # ==============================================================================
  """Core Keras layers.
  """
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import copy
  import sys
  import textwrap
  import types as python_types
  import warnings
  
  import numpy as np
  
  from tensorflow.python.eager import backprop
  from tensorflow.python.eager import context
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.keras import activations
  from tensorflow.python.keras import backend as K
  from tensorflow.python.keras import constraints
  from tensorflow.python.keras import initializers
  from tensorflow.python.keras import regularizers
  from tensorflow.python.keras.engine.base_layer import Layer
  from tensorflow.python.keras.engine.input_spec import InputSpec
  from tensorflow.python.keras.layers.ops import core as core_ops
  from tensorflow.python.keras.utils import conv_utils
  from tensorflow.python.keras.utils import generic_utils
  from tensorflow.python.keras.utils import tf_utils
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn
  from tensorflow.python.ops import variable_scope
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.training.tracking import base as trackable
  from tensorflow.python.util import nest
  from tensorflow.python.util import tf_inspect
  from tensorflow.python.util.tf_export import keras_export
  
  
  # pylint: disable=g-classes-have-attributes
  @keras_export('keras.layers.Masking')
  class Masking(Layer):
    """Masks a sequence by using a mask value to skip timesteps.
  
    For each timestep in the input tensor (dimension #1 in the tensor),
    if all values in the input tensor at that timestep
    are equal to `mask_value`, then the timestep will be masked (skipped)
    in all downstream layers (as long as they support masking).
  
    If any downstream layer does not support masking yet receives such
    an input mask, an exception will be raised.
  
    Example:
  
    Consider a Numpy data array `x` of shape `(samples, timesteps, features)`,
    to be fed to an LSTM layer. You want to mask timestep #3 and #5 because you
    lack data for these timesteps. You can:
  
    - Set `x[:, 3, :] = 0.` and `x[:, 5, :] = 0.`
    - Insert a `Masking` layer with `mask_value=0.` before the LSTM layer:
  
    ```python
    samples, timesteps, features = 32, 10, 8
    inputs = np.random.random([samples, timesteps, features]).astype(np.float32)
    inputs[:, 3, :] = 0.
    inputs[:, 5, :] = 0.
  
    model = tf.keras.models.Sequential()
    model.add(tf.keras.layers.Masking(mask_value=0.,
                                      input_shape=(timesteps, features)))
    model.add(tf.keras.layers.LSTM(32))
  
    output = model(inputs)
    # The time step 3 and 5 will be skipped from LSTM calculation.
    ```
  
    See [the masking and padding guide](
      https://www.tensorflow.org/guide/keras/masking_and_padding)
    for more details.
    """
  
    def __init__(self, mask_value=0., **kwargs):
      super(Masking, self).__init__(**kwargs)
      self.supports_masking = True
      self.mask_value = mask_value
      self._compute_output_and_mask_jointly = True
  
    def compute_mask(self, inputs, mask=None):
      return K.any(math_ops.not_equal(inputs, self.mask_value), axis=-1)
  
    def call(self, inputs):
      boolean_mask = K.any(
          math_ops.not_equal(inputs, self.mask_value), axis=-1, keepdims=True)
      outputs = inputs * math_ops.cast(boolean_mask, inputs.dtype)
      # Compute the mask and outputs simultaneously.
      outputs._keras_mask = array_ops.squeeze(boolean_mask, axis=-1)  # pylint: disable=protected-access
      return outputs
  
    def compute_output_shape(self, input_shape):
      return input_shape
  
    def get_config(self):
      config = {'mask_value': self.mask_value}
      base_config = super(Masking, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.Dropout')
  class Dropout(Layer):
    """Applies Dropout to the input.
  
    The Dropout layer randomly sets input units to 0 with a frequency of `rate`
    at each step during training time, which helps prevent overfitting.
    Inputs not set to 0 are scaled up by 1/(1 - rate) such that the sum over
    all inputs is unchanged.
  
    Note that the Dropout layer only applies when `training` is set to True
    such that no values are dropped during inference. When using `model.fit`,
    `training` will be appropriately set to True automatically, and in other
    contexts, you can set the kwarg explicitly to True when calling the layer.
  
    (This is in contrast to setting `trainable=False` for a Dropout layer.
    `trainable` does not affect the layer's behavior, as Dropout does
    not have any variables/weights that can be frozen during training.)
  
    >>> tf.random.set_seed(0)
    >>> layer = tf.keras.layers.Dropout(.2, input_shape=(2,))
    >>> data = np.arange(10).reshape(5, 2).astype(np.float32)
    >>> print(data)
    [[0. 1.]
     [2. 3.]
     [4. 5.]
     [6. 7.]
     [8. 9.]]
    >>> outputs = layer(data, training=True)
    >>> print(outputs)
    tf.Tensor(
    [[ 0.    1.25]
     [ 2.5   3.75]
     [ 5.    6.25]
     [ 7.5   8.75]
     [10.    0.  ]], shape=(5, 2), dtype=float32)
  
    Arguments:
      rate: Float between 0 and 1. Fraction of the input units to drop.
      noise_shape: 1D integer tensor representing the shape of the
        binary dropout mask that will be multiplied with the input.
        For instance, if your inputs have shape
        `(batch_size, timesteps, features)` and
        you want the dropout mask to be the same for all timesteps,
        you can use `noise_shape=(batch_size, 1, features)`.
      seed: A Python integer to use as random seed.
  
    Call arguments:
      inputs: Input tensor (of any rank).
      training: Python boolean indicating whether the layer should behave in
        training mode (adding dropout) or in inference mode (doing nothing).
    """
  
    def __init__(self, rate, noise_shape=None, seed=None, **kwargs):
      super(Dropout, self).__init__(**kwargs)
      self.rate = rate
      self.noise_shape = noise_shape
      self.seed = seed
      self.supports_masking = True
  
    def _get_noise_shape(self, inputs):
      # Subclasses of `Dropout` may implement `_get_noise_shape(self, inputs)`,
      # which will override `self.noise_shape`, and allows for custom noise
      # shapes with dynamically sized inputs.
      if self.noise_shape is None:
        return None
  
      concrete_inputs_shape = array_ops.shape(inputs)
      noise_shape = []
      for i, value in enumerate(self.noise_shape):
        noise_shape.append(concrete_inputs_shape[i] if value is None else value)
      return ops.convert_to_tensor_v2(noise_shape)
  
    def call(self, inputs, training=None):
      if training is None:
        training = K.learning_phase()
  
      def dropped_inputs():
        return nn.dropout(
            inputs,
            noise_shape=self._get_noise_shape(inputs),
            seed=self.seed,
            rate=self.rate)
  
      output = tf_utils.smart_cond(training,
                                   dropped_inputs,
                                   lambda: array_ops.identity(inputs))
      return output
  
    def compute_output_shape(self, input_shape):
      return input_shape
  
    def get_config(self):
      config = {
          'rate': self.rate,
          'noise_shape': self.noise_shape,
          'seed': self.seed
      }
      base_config = super(Dropout, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.SpatialDropout1D')
  class SpatialDropout1D(Dropout):
    """Spatial 1D version of Dropout.
  
    This version performs the same function as Dropout, however, it drops
    entire 1D feature maps instead of individual elements. If adjacent frames
    within feature maps are strongly correlated (as is normally the case in
    early convolution layers) then regular dropout will not regularize the
    activations and will otherwise just result in an effective learning rate
    decrease. In this case, SpatialDropout1D will help promote independence
    between feature maps and should be used instead.
  
    Arguments:
      rate: Float between 0 and 1. Fraction of the input units to drop.
  
    Call arguments:
      inputs: A 3D tensor.
      training: Python boolean indicating whether the layer should behave in
        training mode (adding dropout) or in inference mode (doing nothing).
  
    Input shape:
      3D tensor with shape:
      `(samples, timesteps, channels)`
  
    Output shape:
      Same as input.
  
    References:
      - [Efficient Object Localization Using Convolutional
        Networks](https://arxiv.org/abs/1411.4280)
    """
  
    def __init__(self, rate, **kwargs):
      super(SpatialDropout1D, self).__init__(rate, **kwargs)
      self.input_spec = InputSpec(ndim=3)
  
    def _get_noise_shape(self, inputs):
      input_shape = array_ops.shape(inputs)
      noise_shape = (input_shape[0], 1, input_shape[2])
      return noise_shape
  
  
  @keras_export('keras.layers.SpatialDropout2D')
  class SpatialDropout2D(Dropout):
    """Spatial 2D version of Dropout.
  
    This version performs the same function as Dropout, however, it drops
    entire 2D feature maps instead of individual elements. If adjacent pixels
    within feature maps are strongly correlated (as is normally the case in
    early convolution layers) then regular dropout will not regularize the
    activations and will otherwise just result in an effective learning rate
    decrease. In this case, SpatialDropout2D will help promote independence
    between feature maps and should be used instead.
  
    Arguments:
      rate: Float between 0 and 1. Fraction of the input units to drop.
      data_format: 'channels_first' or 'channels_last'.
        In 'channels_first' mode, the channels dimension
        (the depth) is at index 1,
        in 'channels_last' mode is it at index 3.
        It defaults to the `image_data_format` value found in your
        Keras config file at `~/.keras/keras.json`.
        If you never set it, then it will be "channels_last".
  
    Call arguments:
      inputs: A 4D tensor.
      training: Python boolean indicating whether the layer should behave in
        training mode (adding dropout) or in inference mode (doing nothing).
  
    Input shape:
      4D tensor with shape:
      `(samples, channels, rows, cols)` if data_format='channels_first'
      or 4D tensor with shape:
      `(samples, rows, cols, channels)` if data_format='channels_last'.
  
    Output shape:
      Same as input.
  
    References:
      - [Efficient Object Localization Using Convolutional
        Networks](https://arxiv.org/abs/1411.4280)
    """
  
    def __init__(self, rate, data_format=None, **kwargs):
      super(SpatialDropout2D, self).__init__(rate, **kwargs)
      if data_format is None:
        data_format = K.image_data_format()
      if data_format not in {'channels_last', 'channels_first'}:
        raise ValueError('data_format must be in '
                         '{"channels_last", "channels_first"}')
      self.data_format = data_format
      self.input_spec = InputSpec(ndim=4)
  
    def _get_noise_shape(self, inputs):
      input_shape = array_ops.shape(inputs)
      if self.data_format == 'channels_first':
        return (input_shape[0], input_shape[1], 1, 1)
      elif self.data_format == 'channels_last':
        return (input_shape[0], 1, 1, input_shape[3])
  
  
  @keras_export('keras.layers.SpatialDropout3D')
  class SpatialDropout3D(Dropout):
    """Spatial 3D version of Dropout.
  
    This version performs the same function as Dropout, however, it drops
    entire 3D feature maps instead of individual elements. If adjacent voxels
    within feature maps are strongly correlated (as is normally the case in
    early convolution layers) then regular dropout will not regularize the
    activations and will otherwise just result in an effective learning rate
    decrease. In this case, SpatialDropout3D will help promote independence
    between feature maps and should be used instead.
  
    Arguments:
      rate: Float between 0 and 1. Fraction of the input units to drop.
      data_format: 'channels_first' or 'channels_last'.
          In 'channels_first' mode, the channels dimension (the depth)
          is at index 1, in 'channels_last' mode is it at index 4.
          It defaults to the `image_data_format` value found in your
          Keras config file at `~/.keras/keras.json`.
          If you never set it, then it will be "channels_last".
  
    Call arguments:
      inputs: A 5D tensor.
      training: Python boolean indicating whether the layer should behave in
        training mode (adding dropout) or in inference mode (doing nothing).
  
    Input shape:
      5D tensor with shape:
      `(samples, channels, dim1, dim2, dim3)` if data_format='channels_first'
      or 5D tensor with shape:
      `(samples, dim1, dim2, dim3, channels)` if data_format='channels_last'.
  
    Output shape:
      Same as input.
  
    References:
      - [Efficient Object Localization Using Convolutional
        Networks](https://arxiv.org/abs/1411.4280)
    """
  
    def __init__(self, rate, data_format=None, **kwargs):
      super(SpatialDropout3D, self).__init__(rate, **kwargs)
      if data_format is None:
        data_format = K.image_data_format()
      if data_format not in {'channels_last', 'channels_first'}:
        raise ValueError('data_format must be in '
                         '{"channels_last", "channels_first"}')
      self.data_format = data_format
      self.input_spec = InputSpec(ndim=5)
  
    def _get_noise_shape(self, inputs):
      input_shape = array_ops.shape(inputs)
      if self.data_format == 'channels_first':
        return (input_shape[0], input_shape[1], 1, 1, 1)
      elif self.data_format == 'channels_last':
        return (input_shape[0], 1, 1, 1, input_shape[4])
  
  
  @keras_export('keras.layers.Activation')
  class Activation(Layer):
    """Applies an activation function to an output.
  
    Arguments:
      activation: Activation function, such as `tf.nn.relu`, or string name of
        built-in activation function, such as "relu".
  
    Usage:
  
    >>> layer = tf.keras.layers.Activation('relu')
    >>> output = layer([-3.0, -1.0, 0.0, 2.0])
    >>> list(output.numpy())
    [0.0, 0.0, 0.0, 2.0]
    >>> layer = tf.keras.layers.Activation(tf.nn.relu)
    >>> output = layer([-3.0, -1.0, 0.0, 2.0])
    >>> list(output.numpy())
    [0.0, 0.0, 0.0, 2.0]
  
    Input shape:
      Arbitrary. Use the keyword argument `input_shape`
      (tuple of integers, does not include the batch axis)
      when using this layer as the first layer in a model.
  
    Output shape:
      Same shape as input.
    """
  
    def __init__(self, activation, **kwargs):
      super(Activation, self).__init__(**kwargs)
      self.supports_masking = True
      self.activation = activations.get(activation)
  
    def call(self, inputs):
      return self.activation(inputs)
  
    def compute_output_shape(self, input_shape):
      return input_shape
  
    def get_config(self):
      config = {'activation': activations.serialize(self.activation)}
      base_config = super(Activation, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.Reshape')
  class Reshape(Layer):
    """Layer that reshapes inputs into the given shape.
  
    Input shape:
      Arbitrary, although all dimensions in the input shape must be known/fixed.
      Use the keyword argument `input_shape` (tuple of integers, does not include
      the samples/batch size axis) when using this layer as the first layer
      in a model.
  
    Output shape:
      `(batch_size,) + target_shape`
  
    Example:
  
    >>> # as first layer in a Sequential model
    >>> model = tf.keras.Sequential()
    >>> model.add(tf.keras.layers.Reshape((3, 4), input_shape=(12,)))
    >>> # model.output_shape == (None, 3, 4), `None` is the batch size.
    >>> model.output_shape
    (None, 3, 4)
  
    >>> # as intermediate layer in a Sequential model
    >>> model.add(tf.keras.layers.Reshape((6, 2)))
    >>> model.output_shape
    (None, 6, 2)
  
    >>> # also supports shape inference using `-1` as dimension
    >>> model.add(tf.keras.layers.Reshape((-1, 2, 2)))
    >>> model.output_shape
    (None, 3, 2, 2)
    """
  
    def __init__(self, target_shape, **kwargs):
      """Creates a `tf.keras.layers.Reshape`  layer instance.
  
      Args:
        target_shape: Target shape. Tuple of integers, does not include the
          samples dimension (batch size).
        **kwargs: Any additional layer keyword arguments.
      """
      super(Reshape, self).__init__(**kwargs)
      self.target_shape = tuple(target_shape)
  
    def _fix_unknown_dimension(self, input_shape, output_shape):
      """Find and replace a missing dimension in an output shape.
  
      This is a near direct port of the internal Numpy function
      `_fix_unknown_dimension` in `numpy/core/src/multiarray/shape.c`
  
      Arguments:
        input_shape: Shape of array being reshaped
        output_shape: Desired shape of the array with at most
          a single -1 which indicates a dimension that should be
          derived from the input shape.
  
      Returns:
        The new output shape with a -1 replaced with its computed value.
  
      Raises:
        ValueError: If the total array size of the output_shape is
        different than the input_shape, or more than one unknown dimension
        is specified.
      """
      output_shape = list(output_shape)
      msg = ('total size of new array must be unchanged, '
             'input_shape = {}, output_shape = {}'
             .format(input_shape, output_shape))
  
      known, unknown = 1, None
      for index, dim in enumerate(output_shape):
        if dim < 0:
          if unknown is None:
            unknown = index
          else:
            raise ValueError('Can only specify one unknown dimension.')
        else:
          known *= dim
  
      original = np.prod(input_shape, dtype=int)
      if unknown is not None:
        if known == 0 or original % known != 0:
          raise ValueError(msg)
        output_shape[unknown] = original // known
      elif original != known:
        raise ValueError(msg)
      return output_shape
  
    def compute_output_shape(self, input_shape):
      input_shape = tensor_shape.TensorShape(input_shape).as_list()
      if None in input_shape[1:]:
        output_shape = [input_shape[0]]
        # input shape (partially) unknown? replace -1's with None's
        output_shape += tuple(s if s != -1 else None for s in self.target_shape)
      else:
        output_shape = [input_shape[0]]
        output_shape += self._fix_unknown_dimension(input_shape[1:],
                                                    self.target_shape)
      return tensor_shape.TensorShape(output_shape)
  
    def call(self, inputs):
      result = array_ops.reshape(
          inputs, (array_ops.shape(inputs)[0],) + self.target_shape)
      if not context.executing_eagerly():
        # Set the static shape for the result since it might lost during array_ops
        # reshape, eg, some `None` dim in the result could be inferred.
        result.set_shape(self.compute_output_shape(inputs.shape))
      return result
  
    def get_config(self):
      config = {'target_shape': self.target_shape}
      base_config = super(Reshape, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.Permute')
  class Permute(Layer):
    """Permutes the dimensions of the input according to a given pattern.
  
    Useful e.g. connecting RNNs and convnets.
  
    Example:
  
    ```python
    model = Sequential()
    model.add(Permute((2, 1), input_shape=(10, 64)))
    # now: model.output_shape == (None, 64, 10)
    # note: `None` is the batch dimension
    ```
  
    Arguments:
      dims: Tuple of integers. Permutation pattern does not include the
        samples dimension. Indexing starts at 1.
        For instance, `(2, 1)` permutes the first and second dimensions
        of the input.
  
    Input shape:
      Arbitrary. Use the keyword argument `input_shape`
      (tuple of integers, does not include the samples axis)
      when using this layer as the first layer in a model.
  
    Output shape:
      Same as the input shape, but with the dimensions re-ordered according
      to the specified pattern.
    """
  
    def __init__(self, dims, **kwargs):
      super(Permute, self).__init__(**kwargs)
      self.dims = tuple(dims)
      if sorted(dims) != list(range(1, len(dims) + 1)):
        raise ValueError(
            'Invalid permutation `dims` for Permute Layer: %s. '
            'The set of indices in `dims` must be consecutive and start from 1.' %
            (dims,))
      self.input_spec = InputSpec(ndim=len(self.dims) + 1)
  
    def compute_output_shape(self, input_shape):
      input_shape = tensor_shape.TensorShape(input_shape).as_list()
      output_shape = copy.copy(input_shape)
      for i, dim in enumerate(self.dims):
        target_dim = input_shape[dim]
        output_shape[i + 1] = target_dim
      return tensor_shape.TensorShape(output_shape)
  
    def call(self, inputs):
      return array_ops.transpose(inputs, perm=(0,) + self.dims)
  
    def get_config(self):
      config = {'dims': self.dims}
      base_config = super(Permute, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.Flatten')
  class Flatten(Layer):
    """Flattens the input. Does not affect the batch size.
  
    Note: If inputs are shaped `(batch,)` without a feature axis, then
    flattening adds an extra channel dimension and output shape is `(batch, 1)`.
  
    Arguments:
      data_format: A string,
        one of `channels_last` (default) or `channels_first`.
        The ordering of the dimensions in the inputs.
        `channels_last` corresponds to inputs with shape
        `(batch, ..., channels)` while `channels_first` corresponds to
        inputs with shape `(batch, channels, ...)`.
        It defaults to the `image_data_format` value found in your
        Keras config file at `~/.keras/keras.json`.
        If you never set it, then it will be "channels_last".
  
    Example:
  
    >>> model = tf.keras.Sequential()
    >>> model.add(tf.keras.layers.Conv2D(64, 3, 3, input_shape=(3, 32, 32)))
    >>> model.output_shape
    (None, 1, 10, 64)
  
    >>> model.add(Flatten())
    >>> model.output_shape
    (None, 640)
  
    """
  
    def __init__(self, data_format=None, **kwargs):
      super(Flatten, self).__init__(**kwargs)
      self.data_format = conv_utils.normalize_data_format(data_format)
      self.input_spec = InputSpec(min_ndim=1)
  
    def call(self, inputs):
      if (self.data_format == 'channels_first'
          and K.ndim(inputs) is not None and K.ndim(inputs) > 1):
        permutation = [0]
        permutation.extend(range(2, K.ndim(inputs)))
        permutation.append(1)
        inputs = array_ops.transpose(inputs, perm=permutation)
  
      input_shape = inputs.shape
      if input_shape[1:].is_fully_defined():
        flattened_dim = tensor_shape.dimension_value(
            np.prod(input_shape[1:], dtype=int))
        # Temporary fix for integer overflow issue.
        if flattened_dim > np.iinfo(np.int32).max:
          shape_dtype = dtypes.int64
        else:
          shape_dtype = dtypes.int32
        outputs = array_ops.reshape(
            inputs, constant_op.constant((-1, flattened_dim), dtype=shape_dtype))
      else:
        batch_size = tensor_shape.dimension_value(inputs.shape[0])
        if batch_size:
          # Temporary fix for integer overflow issue.
          if batch_size > np.iinfo(np.int32).max:
            shape_dtype = dtypes.int64
          else:
            shape_dtype = dtypes.int32
          outputs = array_ops.reshape(
              inputs, constant_op.constant((batch_size, -1), dtype=shape_dtype))
        else:
          outputs = array_ops.reshape(inputs, (array_ops.shape(inputs)[0], -1))
      if not context.executing_eagerly():
        outputs.set_shape(self.compute_output_shape(inputs.shape))
      return outputs
  
    def compute_output_shape(self, input_shape):
      input_shape = tensor_shape.as_shape(input_shape).as_list()
      if not input_shape:
        output_shape = tensor_shape.TensorShape([1])
      else:
        output_shape = [input_shape[0]]
      if np.all(input_shape[1:]):
        output_shape += [np.prod(input_shape[1:], dtype=int)]
      else:
        output_shape += [None]
      return tensor_shape.TensorShape(output_shape)
  
    def get_config(self):
      config = {'data_format': self.data_format}
      base_config = super(Flatten, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.RepeatVector')
  class RepeatVector(Layer):
    """Repeats the input n times.
  
    Example:
  
    ```python
    model = Sequential()
    model.add(Dense(32, input_dim=32))
    # now: model.output_shape == (None, 32)
    # note: `None` is the batch dimension
  
    model.add(RepeatVector(3))
    # now: model.output_shape == (None, 3, 32)
    ```
  
    Arguments:
      n: Integer, repetition factor.
  
    Input shape:
      2D tensor of shape `(num_samples, features)`.
  
    Output shape:
      3D tensor of shape `(num_samples, n, features)`.
    """
  
    def __init__(self, n, **kwargs):
      super(RepeatVector, self).__init__(**kwargs)
      self.n = n
      self.input_spec = InputSpec(ndim=2)
  
    def compute_output_shape(self, input_shape):
      input_shape = tensor_shape.TensorShape(input_shape).as_list()
      return tensor_shape.TensorShape([input_shape[0], self.n, input_shape[1]])
  
    def call(self, inputs):
      return K.repeat(inputs, self.n)
  
    def get_config(self):
      config = {'n': self.n}
      base_config = super(RepeatVector, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
  
  @keras_export('keras.layers.Lambda')
  class Lambda(Layer):
    """Wraps arbitrary expressions as a `Layer` object.
  
    The `Lambda` layer exists so that arbitrary TensorFlow functions
    can be used when constructing `Sequential` and Functional API
    models. `Lambda` layers are best suited for simple operations or
    quick experimentation. For more advanced use cases, follow
    [this guide](https://www.tensorflow.org/guide/keras/custom_layers_and_models)
    for subclassing `tf.keras.layers.Layer`.
  
    The main reason to subclass `tf.keras.layers.Layer` instead of using a
    `Lambda` layer is saving and inspecting a Model. `Lambda` layers
    are saved by serializing the Python bytecode, whereas subclassed
    Layers can be saved via overriding their `get_config` method. Overriding
    `get_config` improves the portability of Models. Models that rely on
    subclassed Layers are also often easier to visualize and reason about.
  
    Examples:
  
    ```python
    # add a x -> x^2 layer
    model.add(Lambda(lambda x: x ** 2))
    ```
    ```python
    # add a layer that returns the concatenation
    # of the positive part of the input and
    # the opposite of the negative part
  
    def antirectifier(x):
        x -= K.mean(x, axis=1, keepdims=True)
        x = K.l2_normalize(x, axis=1)
        pos = K.relu(x)
        neg = K.relu(-x)
        return K.concatenate([pos, neg], axis=1)
  
    model.add(Lambda(antirectifier))
    ```
  
    Variables:
      While it is possible to use Variables with Lambda layers, this practice is
      discouraged as it can easily lead to bugs. For instance, consider the
      following layer:
  
      ```python
        scale = tf.Variable(1.)
        scale_layer = tf.keras.layers.Lambda(lambda x: x * scale)
      ```
  
      Because scale_layer does not directly track the `scale` variable, it will
      not appear in `scale_layer.trainable_weights` and will therefore not be
      trained if `scale_layer` is used in a Model.
  
      A better pattern is to write a subclassed Layer:
  
      ```python
        class ScaleLayer(tf.keras.layers.Layer):
          def __init__(self):
            super(ScaleLayer, self).__init__()
            self.scale = tf.Variable(1.)
  
          def call(self, inputs):
            return inputs * self.scale
      ```
  
      In general, Lambda layers can be convenient for simple stateless
      computation, but anything more complex should use a subclass Layer instead.
  
    Arguments:
      function: The function to be evaluated. Takes input tensor as first
        argument.
      output_shape: Expected output shape from function. This argument can be
        inferred if not explicitly provided. Can be a tuple or function. If a
        tuple, it only specifies the first dimension onward;
        sample dimension is assumed either the same as the input: `output_shape =
          (input_shape[0], ) + output_shape` or, the input is `None` and
        the sample dimension is also `None`: `output_shape = (None, ) +
          output_shape` If a function, it specifies the entire shape as a function
          of the
        input shape: `output_shape = f(input_shape)`
      mask: Either None (indicating no masking) or a callable with the same
        signature as the `compute_mask` layer method, or a tensor that will be
        returned as output mask regardless of what the input is.
      arguments: Optional dictionary of keyword arguments to be passed to the
        function.
    Input shape: Arbitrary. Use the keyword argument input_shape (tuple of
      integers, does not include the samples axis) when using this layer as the
      first layer in a model.
    Output shape: Specified by `output_shape` argument
    """
  
    @trackable.no_automatic_dependency_tracking
    def __init__(self, function, output_shape=None, mask=None, arguments=None,
                 **kwargs):
      super(Lambda, self).__init__(**kwargs)
  
      self.arguments = arguments or {}
      self.function = function
  
      if mask is not None:
        self.supports_masking = True
      self.mask = mask
      self._output_shape = output_shape
  
      # Warning on every invocation will be quite irksome in Eager mode.
      self._already_warned = False
  
      function_args = tf_inspect.getfullargspec(function).args
      self._fn_expects_training_arg = 'training' in function_args
      self._fn_expects_mask_arg = 'mask' in function_args
  
    @tf_utils.shape_type_conversion
    def compute_output_shape(self, input_shape):
      if self._output_shape is None:
        # Make use of existing autocomputation but provide Lambda-specific
        # error message. This is always safe to run even when the outer context
        # is Graph mode because Lambda layers don't have side effects such as
        # `add_loss`.
        with context.eager_mode():
          try:
            return super(Lambda, self).compute_output_shape(input_shape)
          except NotImplementedError:
            raise NotImplementedError(
                'We could not automatically infer the shape of the Lambda\'s '
                'output. Please specify `output_shape` for this Lambda.')
  
      if callable(self._output_shape):
        output_shapes = self._output_shape(input_shape)
        return tf_utils.convert_shapes(output_shapes, to_tuples=False)
  
      # Output shapes are passed directly and don't include batch dimension.
      input_tensor_shape = tf_utils.convert_shapes(input_shape, to_tuples=False)
      batch_size = nest.flatten(input_tensor_shape)[0][0] if input_shape else None
  
      def _add_batch(shape):
        return tensor_shape.TensorShape([batch_size] + shape.as_list())
  
      output_shapes = tf_utils.convert_shapes(self._output_shape, to_tuples=False)
      return nest.map_structure(_add_batch, output_shapes)
  
    def call(self, inputs, mask=None, training=None):
      # We must copy for thread safety, but it only needs to be a shallow copy.
      kwargs = {k: v for k, v in self.arguments.items()}
      if self._fn_expects_mask_arg:
        kwargs['mask'] = mask
      if self._fn_expects_training_arg:
        kwargs['training'] = training
  
      created_variables = []
      def _variable_creator(next_creator, **kwargs):
        var = next_creator(**kwargs)
        created_variables.append(var)
        return var
  
      with backprop.GradientTape(watch_accessed_variables=True) as tape,\
          variable_scope.variable_creator_scope(_variable_creator):
        result = self.function(inputs, **kwargs)
      self._check_variables(created_variables, tape.watched_variables())
      return result
  
    def _check_variables(self, created_variables, accessed_variables):
      if not created_variables and not accessed_variables:
        # In the common case that a Lambda layer does not touch a Variable, we
        # don't want to incur the runtime cost of assembling any state used for
        # checking only to immediately discard it.
        return
  
      tracked_weights = set(v.ref() for v in self.weights)
      untracked_new_vars = [
          v for v in created_variables if v.ref() not in tracked_weights
      ]
      if untracked_new_vars:
        variable_str = '\n'.join('  {}'.format(i) for i in untracked_new_vars)
        error_str = textwrap.dedent(
            '''
            The following Variables were created within a Lambda layer ({name})
            but are not tracked by said layer:
            {variable_str}
            The layer cannot safely ensure proper Variable reuse across multiple
            calls, and consquently this behavior is disallowed for safety. Lambda
            layers are not well suited to stateful computation; instead, writing a
            subclassed Layer is the recommend way to define layers with
            Variables.'''
        ).format(name=self.name, variable_str=variable_str)
        raise ValueError(error_str)
  
      untracked_used_vars = [
          v for v in accessed_variables if v.ref() not in tracked_weights
      ]
      if untracked_used_vars and not self._already_warned:
        variable_str = '\n'.join('  {}'.format(i) for i in untracked_used_vars)
        self._warn(textwrap.dedent(
            '''
            The following Variables were used a Lambda layer's call ({name}), but
            are not present in its tracked objects:
            {variable_str}
            It is possible that this is intended behavior, but it is more likely
            an omission. This is a strong indication that this layer should be
            formulated as a subclassed Layer rather than a Lambda layer.'''
        ).format(name=self.name, variable_str=variable_str))
        self._already_warned = True
  
    def _warn(self, msg):
      # This method will be overridden in a unit test to raise an error, because
      # self.assertWarns is not universally implemented.
      return tf_logging.warn(msg)
  
    def compute_mask(self, inputs, mask=None):
      if callable(self.mask):
        return self.mask(inputs, mask)
      return self.mask
  
    def get_config(self):
      function_config = self._serialize_function_to_config(self.function)
      output_shape_config = self._serialize_function_to_config(self._output_shape,
                                                               allow_raw=True)
      config = {
          'function': function_config[0],
          'function_type': function_config[1],
          'module': function_config[2],
          'output_shape': output_shape_config[0],
          'output_shape_type': output_shape_config[1],
          'output_shape_module': output_shape_config[2],
      }
      if self.mask is not None:
        mask_config = self._serialize_function_to_config(self.mask)
        config.update({
            'mask': mask_config[0],
            'mask_type': mask_config[1],
            'mask_module': mask_config[2]
        })
      config['arguments'] = self.arguments
  
      base_config = super(Lambda, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  
    def _serialize_function_to_config(self, inputs, allow_raw=False):
      if isinstance(inputs, python_types.LambdaType):
        output = generic_utils.func_dump(inputs)
        output_type = 'lambda'
        module = inputs.__module__
      elif callable(inputs):
        output = inputs.__name__
        output_type = 'function'
        module = inputs.__module__
      elif allow_raw:
        output = inputs
        output_type = 'raw'
        module = None
      else:
        raise ValueError(
            'Invalid input for serialization, type: %s ' % type(inputs))
  
      return output, output_type, module
  
    @classmethod
    def from_config(cls, config, custom_objects=None):
      config = config.copy()
      function = cls._parse_function_from_config(
          config, custom_objects, 'function', 'module', 'function_type')
  
      output_shape = cls._parse_function_from_config(
          config, custom_objects, 'output_shape', 'output_shape_module',
          'output_shape_type')
      if 'mask' in config:
        mask = cls._parse_function_from_config(
            config, custom_objects, 'mask', 'mask_module', 'mask_type')
      else:
        mask = None
  
      config['function'] = function
      config['output_shape'] = output_shape
      config['mask'] = mask
  
      # If arguments were numpy array, they have been saved as
      # list. We need to recover the ndarray
      if 'arguments' in config:
        for key in config['arguments']:
          if isinstance(config['arguments'][key], dict):
            arg_dict = config['arguments'][key]
            if 'type' in arg_dict and arg_dict['type'] == 'ndarray':
              # Overwrite the argument with its numpy translation
              config['arguments'][key] = np.array(arg_dict['value'])
  
      return cls(**config)
  
    @classmethod
    def _parse_function_from_config(
        cls, config, custom_objects, func_attr_name, module_attr_name,
        func_type_attr_name):
      globs = globals()
      module = config.pop(module_attr_name, None)
      if module in sys.modules:
        globs.update(sys.modules[module].__dict__)
      elif module is not None:
        # Note: we don't know the name of the function if it's a lambda.
        warnings.warn('{} is not loaded, but a Lambda layer uses it. '
                      'It may cause errors.'.format(module)
                      , UserWarning)
      if custom_objects:
        globs.update(custom_objects)
      function_type = config.pop(func_type_attr_name)
      if function_type == 'function':
        # Simple lookup in custom objects
        function = generic_utils.deserialize_keras_object(
            config[func_attr_name],
            custom_objects=custom_objects,
            printable_module_name='function in Lambda layer')
      elif function_type == 'lambda':
        # Unsafe deserialization from bytecode
        function = generic_utils.func_load(
            config[func_attr_name], globs=globs)
      elif function_type == 'raw':
        function = config[func_attr_name]
      else:
        raise TypeError('Unknown function type:', function_type)
      return function
  
  
  @keras_export('keras.layers.Dense')
  class Dense(Layer):
    """Just your regular densely-connected NN layer.
  
    `Dense` implements the operation:
    `output = activation(dot(input, kernel) + bias)`
    where `activation` is the element-wise activation function
    passed as the `activation` argument, `kernel` is a weights matrix
    created by the layer, and `bias` is a bias vector created by the layer
    (only applicable if `use_bias` is `True`).
  
    Note: If the input to the layer has a rank greater than 2, then `Dense`
    computes the dot product between the `inputs` and the `kernel` along the
    last axis of the `inputs` and axis 1 of the `kernel` (using `tf.tensordot`).
    For example, if input has dimensions `(batch_size, d0, d1)`,
    then we create a `kernel` with shape `(d1, units)`, and the `kernel` operates
    along axis 2 of the `input`, on every sub-tensor of shape `(1, 1, d1)`
    (there are `batch_size * d0` such sub-tensors).
    The output in this case will have shape `(batch_size, d0, units)`.
  
    Besides, layer attributes cannot be modified after the layer has been called
    once (except the `trainable` attribute).
  
    Example:
  
    >>> # Create a `Sequential` model and add a Dense layer as the first layer.
    >>> model = tf.keras.models.Sequential()
    >>> model.add(tf.keras.Input(shape=(16,)))
    >>> model.add(tf.keras.layers.Dense(32, activation='relu'))
    >>> # Now the model will take as input arrays of shape (None, 16)
    >>> # and output arrays of shape (None, 32).
    >>> # Note that after the first layer, you don't need to specify
    >>> # the size of the input anymore:
    >>> model.add(tf.keras.layers.Dense(32))
    >>> model.output_shape
    (None, 32)
  
    Arguments:
      units: Positive integer, dimensionality of the output space.
      activation: Activation function to use.
        If you don't specify anything, no activation is applied
        (ie. "linear" activation: `a(x) = x`).
      use_bias: Boolean, whether the layer uses a bias vector.
      kernel_initializer: Initializer for the `kernel` weights matrix.
      bias_initializer: Initializer for the bias vector.
      kernel_regularizer: Regularizer function applied to
        the `kernel` weights matrix.
      bias_regularizer: Regularizer function applied to the bias vector.
      activity_regularizer: Regularizer function applied to
        the output of the layer (its "activation").
      kernel_constraint: Constraint function applied to
        the `kernel` weights matrix.
      bias_constraint: Constraint function applied to the bias vector.
  
    Input shape:
      N-D tensor with shape: `(batch_size, ..., input_dim)`.
      The most common situation would be
      a 2D input with shape `(batch_size, input_dim)`.
  
    Output shape:
      N-D tensor with shape: `(batch_size, ..., units)`.
      For instance, for a 2D input with shape `(batch_size, input_dim)`,
      the output would have shape `(batch_size, units)`.
    """
  
    def __init__(self,
                 units,
                 activation=None,
                 use_bias=True,
                 kernel_initializer='glorot_uniform',
                 bias_initializer='zeros',
                 kernel_regularizer=None,
                 bias_regularizer=None,
                 activity_regularizer=None,
                 kernel_constraint=None,
                 bias_constraint=None,
                 **kwargs):
      super(Dense, self).__init__(
          activity_regularizer=activity_regularizer, **kwargs)
  
      self.units = int(units) if not isinstance(units, int) else units
      self.activation = activations.get(activation)
      self.use_bias = use_bias
      self.kernel_initializer = initializers.get(kernel_initializer)
      self.bias_initializer = initializers.get(bias_initializer)
      self.kernel_regularizer = regularizers.get(kernel_regularizer)
      self.bias_regularizer = regularizers.get(bias_regularizer)
      self.kernel_constraint = constraints.get(kernel_constraint)
      self.bias_constraint = constraints.get(bias_constraint)
  
      self.input_spec = InputSpec(min_ndim=2)
      self.supports_masking = True
  
    def build(self, input_shape):
      dtype = dtypes.as_dtype(self.dtype or K.floatx())
      if not (dtype.is_floating or dtype.is_complex):
        raise TypeError('Unable to build `Dense` layer with non-floating point '
                        'dtype %s' % (dtype,))
  
      input_shape = tensor_shape.TensorShape(input_shape)
      last_dim = tensor_shape.dimension_value(input_shape[-1])
      if last_dim is None:
        raise ValueError('The last dimension of the inputs to `Dense` '
                         'should be defined. Found `None`.')
      self.input_spec = InputSpec(min_ndim=2, axes={-1: last_dim})
      self.kernel = self.add_weight(
          'kernel',
          shape=[last_dim, self.units],
          initializer=self.kernel_initializer,
          regularizer=self.kernel_regularizer,
          constraint=self.kernel_constraint,
          dtype=self.dtype,
          trainable=True)
      if self.use_bias:
        self.bias = self.add_weight(
            'bias',
            shape=[self.units,],
            initializer=self.bias_initializer,
            regularizer=self.bias_regularizer,
            constraint=self.bias_constraint,
            dtype=self.dtype,
            trainable=True)
      else:
        self.bias = None
      self.built = True
  
    def call(self, inputs):
      return core_ops.dense(
          inputs,
          self.kernel,
          self.bias,
          self.activation,
          dtype=self._compute_dtype_object)
  
    def compute_output_shape(self, input_shape):
      input_shape = tensor_shape.TensorShape(input_shape)
      input_shape = input_shape.with_rank_at_least(2)
      if tensor_shape.dimension_value(input_shape[-1]) is None:
        raise ValueError(
            'The innermost dimension of input_shape must be defined, but saw: %s'
            % input_shape)
      return input_shape[:-1].concatenate(self.units)
  
    def get_config(self):
      config = super(Dense, self).get_config()
      config.update({
          'units':
              self.units,
          'activation':
              activations.serialize(self.activation),
          'use_bias':
              self.use_bias,
          'kernel_initializer':
              initializers.serialize(self.kernel_initializer),
          'bias_initializer':
              initializers.serialize(self.bias_initializer),
          'kernel_regularizer':
              regularizers.serialize(self.kernel_regularizer),
          'bias_regularizer':
              regularizers.serialize(self.bias_regularizer),
          'activity_regularizer':
              regularizers.serialize(self.activity_regularizer),
          'kernel_constraint':
              constraints.serialize(self.kernel_constraint),
          'bias_constraint':
              constraints.serialize(self.bias_constraint)
      })
      return config
  
  
  @keras_export('keras.layers.ActivityRegularization')
  class ActivityRegularization(Layer):
    """Layer that applies an update to the cost function based input activity.
  
    Arguments:
      l1: L1 regularization factor (positive float).
      l2: L2 regularization factor (positive float).
  
    Input shape:
      Arbitrary. Use the keyword argument `input_shape`
      (tuple of integers, does not include the samples axis)
      when using this layer as the first layer in a model.
  
    Output shape:
      Same shape as input.
    """
  
    def __init__(self, l1=0., l2=0., **kwargs):
      super(ActivityRegularization, self).__init__(
          activity_regularizer=regularizers.L1L2(l1=l1, l2=l2), **kwargs)
      self.supports_masking = True
      self.l1 = l1
      self.l2 = l2
  
    def compute_output_shape(self, input_shape):
      return input_shape
  
    def get_config(self):
      config = {'l1': self.l1, 'l2': self.l2}
      base_config = super(ActivityRegularization, self).get_config()
      return dict(list(base_config.items()) + list(config.items()))
  