code: def add_view(self, *args, **kwargs):
          
          try:
              singleton = self.model.objects.get()
          except (self.model.DoesNotExist, self.model.MultipleObjectsReturned):
              kwargs.setdefault("extra_context", {})
              kwargs["extra_context"]["singleton"] = True
              response = super(SingletonAdmin, self).add_view(*args, **kwargs)
              return self.handle_save(args[0], response)
          return redirect(admin_url(self.model, "change", singleton.id))
docs: Redirect to the change view if the singleton instance exists.