def METHOD_NAME(self):
    result = self.exercise({self.set_with_two_of_a_kind})
    deserialised = self.deserialise(result)
    two_of_a_kind_set = deserialised.cfg_set('set_with_two_of_a_kind')
    # test that the configured default value is returned
    second_value = two_of_a_kind_set._cfg_element('a_type')
    self.assertEqual(second_value.raw['some_value'], 42)
    # ensure first_value is also contained in serialisation result (returned from factory)
    first_value = deserialised._cfg_element('a_type', 'first_value_of_a')
    self.assertEqual(first_value.raw['some_value'], 123)
    # ensure the same value is also returned from the cfg_set
    first_value_from_cfg_set = two_of_a_kind_set._cfg_element('a_type', 'first_value_of_a')
    self.assertEqual(first_value.raw, first_value_from_cfg_set.raw)