code: def get_key_by_job_id(cls, mapreduce_id):
      
      return db.Key.from_path(cls.kind(), str(mapreduce_id))
docs: Retrieves the Key for a Job.
  
      Args:
        mapreduce_id: The job to retrieve.
  
      Returns:
        Datastore Key that can be used to fetch the MapreduceState.