old_contents: # Copyright 2016 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.
  # ==============================================================================
  """Converter for slice operations."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import gast
  
  from tensorflow.contrib.autograph.core import converter
  from tensorflow.contrib.autograph.pyct import anno
  from tensorflow.contrib.autograph.pyct import templates
  
  
  class SliceTransformer(converter.Base):
    """Converts slicing operations to their TF counterpart.
  
    Currently, relying on the default slice operator that Tensor uses is
    insufficient, because TensorArray and tensor lists use dedicated index read
    and write functions.
    """
  
    def _process_single_assignment(self, target, value):
      if not isinstance(target, gast.Subscript):
        return None
  
      template = """
        target = ag__.set_item(target, key, item)
      """
      return templates.replace(
          template, target=target.value, key=target.slice, item=value)
  
    def visit_Assign(self, node):
      node = self.generic_visit(node)
      # TODO(mdan): Support unpackings and multiple assignments.
      if len(node.targets) != 1:
        raise NotImplementedError('multiple assignment')
      replacement = self._process_single_assignment(node.targets[0], node.value)
      if replacement is not None:
        return replacement
      return node
  
    def visit_Subscript(self, node):
      node = self.generic_visit(node)
      if not isinstance(node.slice, gast.Index):
        # TODO(mdan): It might make more sense to wave them through.
        raise NotImplementedError('non-index slice')
  
      if not isinstance(node.ctx, gast.Load):
        # Index writes are handled at a higher level, one at which the rvalue is
        # also available.
        return node
  
      dtype = anno.getanno(
          node.value,
          'element_type',
          default=templates.replace_as_expression('None'))
  
      template = """
        ag__.get_item(
            target,
            key,
            opts=ag__.GetItemOpts(element_dtype=dtype))
      """
      return templates.replace_as_expression(
          template, target=node.value, key=node.slice, dtype=dtype)
  
  
  def transform(node, ctx):
    return SliceTransformer(ctx).visit(node)
  
new_contents: # Copyright 2016 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.
  # ==============================================================================
  """Converter for slice operations."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import gast
  
  from tensorflow.contrib.autograph.core import converter
  from tensorflow.contrib.autograph.pyct import anno
  from tensorflow.contrib.autograph.pyct import templates
  
  
  class SliceTransformer(converter.Base):
    """Converts slicing operations to their TF counterpart.
  
    Currently, relying on the default slice operator that Tensor uses is
    insufficient, because TensorArray and tensor lists use dedicated index read
    and write functions.
    """
  
    def _process_single_assignment(self, target, value):
      if not isinstance(target, gast.Subscript):
        return None
  
      template = """
        target = ag__.set_item(target, key, item)
      """
      return templates.replace(
          template, target=target.value, key=target.slice, item=value)
  
    def visit_Assign(self, node):
      node = self.generic_visit(node)
      # TODO(mdan): Support unpackings and multiple assignments.
      if len(node.targets) != 1:
        raise NotImplementedError('multiple assignment')
      replacement = self._process_single_assignment(node.targets[0], node.value)
      if replacement is not None:
        return replacement
      return node
  
    def visit_Subscript(self, node):
      node = self.generic_visit(node)
      if not isinstance(node.slice, gast.Index):
        return node
  
      if not isinstance(node.ctx, gast.Load):
        # Index writes are handled at a higher level, one at which the rvalue is
        # also available.
        return node
  
      dtype = anno.getanno(
          node.value,
          'element_type',
          default=templates.replace_as_expression('None'))
  
      template = """
        ag__.get_item(
            target,
            key,
            opts=ag__.GetItemOpts(element_dtype=dtype))
      """
      return templates.replace_as_expression(
          template, target=node.value, key=node.slice, dtype=dtype)
  
  
  def transform(node, ctx):
    return SliceTransformer(ctx).visit(node)
  
subject: Allow non-index slices to be used without conversion, instead of rejecting them - they are widely used in TF code.