message: Add check for string inputs. If input is string, prompt user to do the string to int conversion in their input_fn.
diff: @@ -20,6 +20,8 @@ from __future__ import print_function
  import collections
  +import six
  +
  from tensorflow.python.estimator import model_fn as model_fn_lib
  from tensorflow.python.feature_column import feature_column as core_fc
  from tensorflow.python.feature_column import feature_column_lib as core_fc_lib
  @@ -289,4 +291,13 @@ def split_inputs(ctx, features, labels):
  for feature_key in tpu_embedding_.feature_to_table_dict:
  sparse_features[feature_key] = features.pop(feature_key)
  + for v in six.itervalues(sparse_features):
  + if not v.dtype.is_integer:
  + raise ValueError('SparseTensor with string as values are not supported. '
  + 'If you are using vocabulary_file_categorical_column or '
  + 'vocabulary_list_categorical_column, please call '
  + 'your_column.categorical_column._transform_feature({'
  + 'your_column.key: features[your_column.key]}) in'
  + 'your input_fn() to convert string to int.')
  +
  return features, labels, sparse_features
  