new_contents: # Copyright 2018 The Lucid 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.
  # ==============================================================================
  
  """Utilities for breaking lists into chunks."""
  
  
  def batch(list, batch_size=None, num_batches=None):
      assert not (batch_size is not None and num_batches)
      if batch_size is not None:
          return _batches_of_max_size(list, batch_size)
      elif num_batches is not None:
          return _n_batches(list, num_batches)
      else:
          raise RuntimeError("Either batch size or num_batches needs to be specified!")
  
  
  def _batches_of_max_size(list, size):
      for i in range(0, len(list), size):
          yield list[i : i + size]
  
  
  def _n_batches(list, size):
      raise NotImplementedError
  
subject: Add beginnings of a batching helper module.