message: Change _TFRecordDataset to be herited from DatasetSource
diff: @@ -74,7 +74,7 @@ class TextLineDataset(dataset_ops.DatasetSource):
  return dtypes.string
  -class _TFRecordDataset(dataset_ops.Dataset):
  +class _TFRecordDataset(dataset_ops.DatasetSource):
  """A `Dataset` comprising records from one or more TFRecord files."""
  def __init__(self, filenames, compression_type=None, buffer_size=None):
  @@ -105,9 +105,6 @@ class _TFRecordDataset(dataset_ops.Dataset):
  return gen_dataset_ops.tf_record_dataset(
  self._filenames, self._compression_type, self._buffer_size)
  - def _inputs(self):
  - return []
  -
  @property
  def output_classes(self):
  return ops.Tensor
  