          self.assertFalse(serializer.is_valid())
          self.assertEqual(serializer.errors, {'target': ['This field may not be null.']})
  
      def test_foreign_key_with_empty(self):
          """
          Regression test for #1072
  
 
</s>
    def test_foreign_key_with_unsaved(self):
        source = ForeignKeySource(name='source-unsaved')
        expected = {'id': None, 'name': 'source-unsaved', 'target': None}

        serializer = ForeignKeySourceSerializer(source)

        # no query if source hasn't been created yet
        with self.assertNumQueries(0):
            self.assertEqual(serializer.data, expected)

          self.assertFalse(serializer.is_valid())
          self.assertEqual(serializer.errors, {'target': ['This field may not be null.']})
  
    def test_foreign_key_with_unsaved(self):
        source = ForeignKeySource(name='source-unsaved')
        expected = {'id': None, 'name': 'source-unsaved', 'target': None}

        serializer = ForeignKeySourceSerializer(source)

        # no query if source hasn't been created yet
        with self.assertNumQueries(0):
            self.assertEqual(serializer.data, expected)

      def test_foreign_key_with_empty(self):
          """
          Regression test for #1072
  
keep keep add keep keep keep keep
 Add support for serializing models with m2m related fields

- In both ManyRelatedField, provide an empty return when trying to
  access a relation field if the instance in question has no PK (so
  likely hasn't been inserted yet)
- Add relevant tests
- Without these changes, exceptions would be raised when trying to
  serialize the uncreated models as it is impossible to query
  relations without a PK
- Add test to ensure RelatedField does not regress as currently 
  supports being serialized with and unsaved model
tests/test_relations_pk.py