text: import pickle
  
  import django
  from django.db import DJANGO_VERSION_PICKLE_KEY, models
  from django.test import SimpleTestCase
  
  
  class ModelPickleTests(SimpleTestCase):
      def test_missing_django_version_unpickling(self):
          """
          #21430 -- Verifies a warning is raised for models that are
          unpickled without a Django version
          """
  
          class MissingDjangoVersion(models.Model):
              title = models.CharField(max_length=10)
  
              def __reduce__(self):
                  reduce_list = super().__reduce__()
                  data = reduce_list[-1]
                  del data[DJANGO_VERSION_PICKLE_KEY]
                  return reduce_list
  
          p = MissingDjangoVersion(title="FooBar")
          msg = "Pickled model instance's Django version is not specified."
          with self.assertRaisesMessage(RuntimeWarning, msg):
              pickle.loads(pickle.dumps(p))
  
      def test_unsupported_unpickle(self):
          """
          #21430 -- Verifies a warning is raised for models that are
          unpickled with a different Django version than the current
          """
  
          class DifferentDjangoVersion(models.Model):
              title = models.CharField(max_length=10)
  
              def __reduce__(self):
                  reduce_list = super().__reduce__()
                  data = reduce_list[-1]
                  data[DJANGO_VERSION_PICKLE_KEY] = "1.0"
                  return reduce_list
  
          p = DifferentDjangoVersion(title="FooBar")
          msg = (
              "Pickled model instance's Django version 1.0 does not match the "
              "current version %s." % django.__version__
          )
          with self.assertRaisesMessage(RuntimeWarning, msg):
              pickle.loads(pickle.dumps(p))
  
      def test_with_getstate(self):
          """
          A model may override __getstate__() to choose the attributes to pickle.
          """
  
          class PickledModel(models.Model):
              def __getstate__(self):
                  state = super().__getstate__().copy()
                  del state["dont_pickle"]
                  return state
  
          m = PickledModel()
          m.dont_pickle = 1
          dumped = pickle.dumps(m)
          self.assertEqual(m.dont_pickle, 1)
          reloaded = pickle.loads(dumped)
          self.assertFalse(hasattr(reloaded, "dont_pickle"))
  