code: def request_job_cancel(self, job_id):
          
          msg = CancelMessage(job_id)
          self.messaging_backend.send(self.worker_mailbox, msg)
          self.storage_backend.mark_job_as_canceling(job_id)
docs: Send a message to the workers to cancel the job with job_id. We then mark the job in the storage
          as being canceled.
  
          :param job_id: the job to cancel
          :return: None