docs: def form_valid(self, form, formsets):
          """
          Response for valid form. In one transaction this will
          save the current form and formsets, log the action
          and message the user.
  
          Returns the results of calling the `success_response` method.
          """
          # check if it's a new object before it save the form
          new_object = False
          if not self.object:
              new_object = True
  
          instance = getattr(form, 'instance', None)
          auto_tags, changed_tags, old_tags = tag_handler.get_tags_from_data(
              form.data, self.get_tags(instance))
          tag_handler.set_auto_tags_for_form(form, auto_tags)
  
          with transaction.commit_on_success():
              self.object = self.save_form(form)
              self.save_formsets(form, formsets, auto_tags=auto_tags)
  
              url = self.get_object_url()
              self.log_action(self.object, CMSLog.SAVE, url=url)
              msg = self.write_message()
  
          # get old and new tags
          if not new_object and changed_tags and old_tags:
              tag_handler.update_changed_tags(changed_tags, old_tags)
  
          return self.success_response(msg)