code: def get_permissions_for_registration(self):
          
          qs = Permission.objects.none()
          for instance in self.modeladmin_instances:
              qs = qs | instance.get_permissions_for_registration()
          return qs
docs: Utilised by Wagtail's 'register_permissions' hook to allow permissions
          for a all models grouped by this class to be assigned to Groups in
          settings.