          model = OneToOneTarget
          fields = ('id', 'name', 'nullable_source')
  
  
  # TODO: Add test that .data cannot be accessed prior to .is_valid
  
  class PKManyToManyTests(TestCase):
      def setUp(self):
          for idx in range(1, 4):
              target = ManyToManyTarget(name='target-%d' % idx)
 
</s> remove     NullableForeignKeySource, NullableOneToOneSource,
 </s> add     NullableForeignKeySource, NullableOneToOneSource, OneToOnePKSource,
class OneToOnePKSourceSerializer(serializers.ModelSerializer):

    class Meta:
        model = OneToOnePKSource
        fields = '__all__'


          model = OneToOneTarget
          fields = ('id', 'name', 'nullable_source')
  
  
class OneToOnePKSourceSerializer(serializers.ModelSerializer):

    class Meta:
        model = OneToOnePKSource
        fields = '__all__'


  # TODO: Add test that .data cannot be accessed prior to .is_valid
  
  class PKManyToManyTests(TestCase):
      def setUp(self):
          for idx in range(1, 4):
              target = ManyToManyTarget(name='target-%d' % idx)
keep keep keep add keep keep keep keep keep keep
 Special case for when OneToOneField is also primary key.

https://github.com/encode/django-rest-framework/issues/5135 
tests/test_relations_pk.py