def testSortingRepeatedCompositeFieldsCustomComparator(self, message_module):
    """Check passing a custom comparator to sort a repeated composite field."""
    message = message_module.TestAllTypes()

    message.repeated_nested_message.add().bb = 1
    message.repeated_nested_message.add().bb = 3
    message.repeated_nested_message.add().bb = 2
    message.repeated_nested_message.add().bb = 6
    message.repeated_nested_message.add().bb = 5
    message.repeated_nested_message.add().bb = 4
    message.repeated_nested_message.sort(key=operator.attrgetter('bb'))
    self.assertEqual(message.repeated_nested_message[0].bb, 1)
    self.assertEqual(message.repeated_nested_message[1].bb, 2)
    self.assertEqual(message.repeated_nested_message[2].bb, 3)
    self.assertEqual(message.repeated_nested_message[3].bb, 4)
    self.assertEqual(message.repeated_nested_message[4].bb, 5)
    self.assertEqual(message.repeated_nested_message[5].bb, 6)
    self.assertEqual(str(message.repeated_nested_message),
                     '[bb: 1\n, bb: 2\n, bb: 3\n, bb: 4\n, bb: 5\n, bb: 6\n]')
Check passing a custom comparator to sort a repeated composite field.
deps/protobuf/python/google/protobuf/internal/message_test.py