code: def exists(self):
          
          r = self._client._redis
          flag = '{}:flag'.format(self._queue)
          return bool(r.exists(flag))
docs: Returns true if the job is still running or zero-os still knows about this job ID
  
          After a job is finished, a job remains on zero-os for max of 5min where you still can read the job result
          after the 5 min is gone, the job result is no more fetchable
          :return: bool