code: def __get_state_by_id(cls, job_id):
      
      state = model.MapreduceState.get_by_job_id(job_id)
      if state is None:
        raise ValueError("Job state for job %s is missing." % job_id)
      return state
docs: Get job state by id.
  
      Args:
        job_id: job id.
  
      Returns:
        model.MapreduceState for the job.
  
      Raises:
        ValueError: if the job state is missing.