message: Remove deprecated WAVDataset
  WAVDataset has been replaced with tfio.IODataset.from_audio
  so this PR removes it. (as otherwise it causes one error in
diff: # limitations under the License.
  # ==============================================================================
  """Audio Dataset.
  -
  -@@WAVDataset
  """
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  -from tensorflow_io.audio.python.ops.audio_ops import WAVDataset
  -
  from tensorflow.python.util.all_util import remove_undocumented
  _allowed_symbols = [
  