def change_min_part_hours(self, min_part_hours):
        self.min_part_hours = min_part_hours
ModelMock members are Mocks, not the actual model members.
dataset/ETHPy150Open openstack/swift/swift/common/ring/builder.py/RingBuilder.change_min_part_hours--crossover with--dataset/ETHPy150Open dcramer/mock-django/tests/mock_django/models/tests.py/ModelMockTestCase.test_model_attrs_are_mocks