docs: def register(**kwargs):
      """Registers a notification_cls.
      """
  
      def _wrapper(notification_cls):
  
          if not issubclass(notification_cls, (Notification,)):
              raise RegisterNotificationError(
                  f"Wrapped class must be a 'Notification' class. "
                  f"Got '{notification_cls.__name__}'"
              )
          site_notifications.register(notification_cls=notification_cls)
          return notification_cls
  
      return _wrapper