def next(self):
    """Returns the next input from this input reader.

    Returns:
      The next input read by this input reader. The return value is
      fed into mapper.

    Raises:
      StopIteration when no more item is left.
    """
    raise NotImplementedError(self.__class__ % "next() not implemented in %s")
dataset/ETHPy150Open GoogleCloudPlatform/appengine-mapreduce/python/src/mapreduce/api/map_job/input_reader.py/InputReader.next/swapped operands of `%`