                  app_label = "model_validation"
  
          apps.lazy_model_operation(dummy_function, ('auth', 'imaginarymodel'))
          apps.lazy_model_operation(dummy_function, ('fanciful_app', 'imaginarymodel'))
  
          post_init.connect(dummy_function, sender='missing-app.Model', apps=apps)
          post_init.connect(DummyClass(), sender='missing-app.Model', apps=apps)
 
</s> remove         errors = _check_lazy_references(apps)
 </s> add         post_init.connect(dummy_function, sender='missing-app.Model', apps=apps)
        post_init.connect(DummyClass(), sender='missing-app.Model', apps=apps)
        post_init.connect(DummyClass().dummy_method, sender='missing-app.Model', apps=apps) </s> remove         msg = "Specified sender must either be a model or a model name of the 'app_label.ModelName' form."
 </s> add         msg = "Invalid model reference 'invalid'. String model references must be of the form 'app_label.ModelName'." </s> remove             self.receiver, sender='signals.Created', weak=False
 </s> add             self.receiver, sender='signals.Created', weak=False, apps=apps </s> remove     @isolate_apps('signals')
    def test_not_loaded_model(self):
 </s> add     @isolate_apps('signals', kwarg_name='apps')
    def test_not_loaded_model(self, apps):
        class DummyClass(object):
            def __call__(self, **kwargs):
                pass

            def dummy_method(self):
                pass

        def dummy_function(*args, **kwargs):
            pass

                  app_label = "model_validation"
  
        class DummyClass(object):
            def __call__(self, **kwargs):
                pass

            def dummy_method(self):
                pass

        def dummy_function(*args, **kwargs):
            pass

          apps.lazy_model_operation(dummy_function, ('auth', 'imaginarymodel'))
          apps.lazy_model_operation(dummy_function, ('fanciful_app', 'imaginarymodel'))
  
          post_init.connect(dummy_function, sender='missing-app.Model', apps=apps)
          post_init.connect(DummyClass(), sender='missing-app.Model', apps=apps)
keep add keep keep keep keep keep
 Fixed #26421 -- Refactored ModelSignal to use Apps.lazy_model_operation() 
tests/model_validation/tests.py