code: def has_storage(func):
      
      @wraps(func)
      def wrapped(*args, **kwargs):
          me = args[0]
          if not hasattr(me, '_storage') or \
                  not me._storage:
              raise exceptions.ImproperConfigurationError(
                  'No storage backend attached to schema <{0}>.'
                      .format(me._name.upper())
              )
          return func(*args, **kwargs)
      return wrapped
docs: Ensure that self/cls contains a Storage backend.