code: def register(self, notification_cls=None):
          
          self.loaded = True
          display_names = [n.display_name for n in self.registry.values()]
          if (
              notification_cls.name not in self.registry
              and notification_cls.display_name not in display_names
          ):
              self.registry.update({notification_cls.name: notification_cls})
  
              models = getattr(notification_cls, "models", [])
              if not models and getattr(notification_cls, "model", None):
                  models = [getattr(notification_cls, "model")]
              for model in models:
                  try:
                      if notification_cls.name not in [
                          n.name for n in self.models[model]
                      ]:
                          self.models[model].append(notification_cls)
                  except KeyError:
                      self.models.update({model: [notification_cls]})
          else:
              raise AlreadyRegistered(
                  f"Notification {notification_cls.name}: "
                  f"{notification_cls.display_name} is already registered."
              )
docs: Registers a Notification class unique by name.