          of relationships.
          """
          data = {'id': 4, 'name': u'source-4', 'target': ''}
          expected_data = {'id': 4, 'name': u'source-4', 'target': None}
          serializer = NullableSlugSourceSerializer(data=data)
          self.assertTrue(serializer.is_valid())
          obj = serializer.save()
          self.assertEquals(serializer.data, expected_data)
          self.assertEqual(obj.name, u'source-4')
  
 
</s> remove         serializer = NullableSlugSourceSerializer(data=data)
 </s> add         serializer = NullableForeignKeySourceSerializer(data=data) </s> remove         serializer = NullableSlugSourceSerializer(instance, data=data)
 </s> add         serializer = NullableForeignKeySourceSerializer(instance, data=data) </s> remove         serializer = NullableSlugSourceSerializer(queryset)
 </s> add         serializer = NullableForeignKeySourceSerializer(queryset) </s> remove         serializer = NullableSlugSourceSerializer(queryset)
 </s> add         serializer = NullableForeignKeySourceSerializer(queryset) </s> remove         serializer = NullableSlugSourceSerializer(instance, data=data)
 </s> add         serializer = NullableForeignKeySourceSerializer(instance, data=data)
        serializer = NullableForeignKeySourceSerializer(data=data)
          of relationships.
          """
          data = {'id': 4, 'name': u'source-4', 'target': ''}
          expected_data = {'id': 4, 'name': u'source-4', 'target': None}
        serializer = NullableForeignKeySourceSerializer(data=data)
          self.assertTrue(serializer.is_valid())
          obj = serializer.save()
          self.assertEquals(serializer.data, expected_data)
          self.assertEqual(obj.name, u'source-4')
  
keep keep keep keep replace keep keep keep keep keep
 Raise Validation Errors when relationships receive incorrect types. Fixes #590. 
rest_framework/tests/relations_slug.py