message: Avoid modifying items in dataset_data_provider.
diff: @@ -96,12 +96,12 @@ class DatasetDataProvider(data_provider.DataProvider):
  items = dataset.decoder.list_items()
  tensors = dataset.decoder.decode(data, items)
  - if record_key in items:
  + items_to_tensors = dict(zip(items, tensors))
  + if record_key in items_to_tensors:
  raise ValueError('The item name used for `record_key` cannot also be '
  'used for a dataset item: %s', record_key)
  - items.append(record_key)
  - tensors.append(key)
  + items_to_tensors[record_key] = key
  super(DatasetDataProvider, self).__init__(
  - items_to_tensors=dict(zip(items, tensors)),
  + items_to_tensors=items_to_tensors,
  num_samples=dataset.num_samples)
  