code: def __add_kickoff_task(cls, job_config, mapreduce_spec):
      
      params = {"mapreduce_id": job_config.job_id}
      # Task is not named so that it can be added within a transaction.
      kickoff_task = taskqueue.Task(
          # TODO(user): Perhaps make this url a computed field of job_config.
          url=job_config._base_path + "/kickoffjob_callback/" + job_config.job_id,
          headers=util._get_task_headers(job_config.job_id),
          params=params)
      if job_config._hooks_cls:
        hooks = job_config._hooks_cls(mapreduce_spec)
        try:
          hooks.enqueue_kickoff_task(kickoff_task, job_config.queue_name)
          return
        except NotImplementedError:
          pass
      kickoff_task.add(job_config.queue_name, transactional=True)
docs: Add kickoff task to taskqueue.
  
      Args:
        job_config: map_job.JobConfig.
        mapreduce_spec: model.MapreduceSpec,