'Retrieves the Key for a mapreduce ID.
Args:
mapreduce_id: The job to fetch.
Returns:
Datastore Key for the command for the given job ID.'

@classmethod
def get_key_by_job_id(cls, mapreduce_id):

    return db.Key.from_path(cls.kind(), ('%s:%s' % (mapreduce_id, cls._KEY_NAME)))
