code: def schedule(cls, mapreduce_spec):
      
      task_name = mapreduce_spec.mapreduce_id + "-finalize"
      finalize_task = taskqueue.Task(
          name=task_name,
          url=(mapreduce_spec.params["base_path"] + "/finalizejob_callback/" +
               mapreduce_spec.mapreduce_id),
          params={"mapreduce_id": mapreduce_spec.mapreduce_id},
          headers=util._get_task_headers(mapreduce_spec.mapreduce_id))
      queue_name = util.get_queue_name(None)
      if not _run_task_hook(mapreduce_spec.get_hooks(),
                            "enqueue_controller_task",
                            finalize_task,
                            queue_name):
        try:
          finalize_task.add(queue_name)
        except (taskqueue.TombstonedTaskError,
                taskqueue.TaskAlreadyExistsError), e:
          logging.warning("Task %r already exists. %s: %s",
                          task_name, e.__class__, e)
docs: Schedule finalize task.
  
      Args:
        mapreduce_spec: mapreduce specification as MapreduceSpec.