@classmethod
  def get_filenames(cls, mapreduce_state):
    """Obtain output filenames from mapreduce state.

    This method should only be called when a MR is finished. Implementors of
    this method should not assume any other methods of this class have been
    called. In the case of no input data, no other method except validate
    would have been called.

    Args:
      mapreduce_state: an instance of model.MapreduceState

    Returns:
      List of filenames this mapreduce successfully wrote to. The list can be
    empty if no output file was successfully written.
    """
    raise NotImplementedError(cls % "get_filenames() not implemented in %s")

  # pylint: disable=unused-argument
dataset/ETHPy150Open GoogleCloudPlatform/appengine-mapreduce/python/src/mapreduce/output_writers.py/OutputWriter.get_filenames/swapped operands of `%`