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.
  # ==============================================================================
  """Implements the graph generation for computation of gradients."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  # pylint: disable=unused-import
  from tensorflow.python.ops.custom_gradient import custom_gradient
  from tensorflow.python.ops.gradients_impl import AggregationMethod
  from tensorflow.python.ops.gradients_impl import gradients
  from tensorflow.python.ops.gradients_impl import hessians
  # pylint: enable=unused-import
  from tensorflow.python.util.all_util import remove_undocumented
  
  _allowed_symbols = [
      # TODO(drpng): find a good place to reference this.
      "AggregationMethod",
      "custom_gradient",
      "gradients",  # tf.gradients.gradients.
      "hessians",  # tf.gradients.hessians
  ]
  remove_undocumented(__name__, _allowed_symbols)
  