code: def _select_manager(backend_name):
      
      if backend_name == 'RedisBackend':
          lock_manager = _LockManagerRedis
      elif backend_name == 'DatabaseBackend':
          lock_manager = _LockManagerDB
      else:
          raise NotImplementedError
      return lock_manager
docs: Select the proper LockManager based on the current backend used by Celery.
  
      :raise NotImplementedError: If Celery is using an unsupported backend.
  
      :param str backend_name: Class name of the current Celery backend. Usually value of
          current_app.extensions['celery'].celery.backend.__class__.__name__.
  
      :return: Class definition object (not instance). One of the _LockManager* classes.