          serialized fields
          """
          child = ChildModel(name1='parent name', name2='child name')
          serializer = DerivedModelSerializer(child)
          assert set(serializer.data.keys()) == {'name1', 'name2', 'id'}
  
      def test_onetoone_primary_key_model_fields_as_expected(self):
          """
          Assert that a model with a onetoone field that is the primary key is
          not treated like a derived model
 
</s> remove         self.assertEqual(set(serializer.data.keys()),
 </s> add         self.assertEqual(set(serializer.data), </s> remove         assert set(serializer.data.keys()) == {'name', 'ref'}
 </s> add         assert set(serializer.data) == {'name', 'ref'} </s> remove             list(self.Meta.model._meta.parents.keys())
 </s> add             list(self.Meta.model._meta.parents) </s> remove         assert list(response.data['actions'].keys()) == ['PUT']
 </s> add         assert list(response.data['actions']) == ['PUT'] </s> remove         assert list(request.POST.keys()) == []
        assert list(request.FILES.keys()) == ['upload']
 </s> add         assert list(request.POST) == []
        assert list(request.FILES) == ['upload']
        assert set(serializer.data) == {'name1', 'name2', 'id'}
          serialized fields
          """
          child = ChildModel(name1='parent name', name2='child name')
          serializer = DerivedModelSerializer(child)
        assert set(serializer.data) == {'name1', 'name2', 'id'}
  
      def test_onetoone_primary_key_model_fields_as_expected(self):
          """
          Assert that a model with a onetoone field that is the primary key is
          not treated like a derived model
keep keep keep keep replace keep keep keep keep keep
 Perfer iter(dict) over iter(dict.keys()) (#5736)

Calling dict.keys() is unnecessary. The two are functionally equivalent
on modern Pythons.

Inspired by Lennart Regebro's talk "Prehistoric Patterns in Python" from
PyCon 2017.

https://www.youtube.com/watch?v=V5-JH23Vk0I 
tests/test_multitable_inheritance.py