def __random_string(size=6):
    return 'RS-' + ''.join(
        random.choice(string.ascii_uppercase + string.digits)
        for x in range(size)
    )
Invaiants can be deined in line
dataset/ETHPy150Open saltstack/salt/tests/integration/modules/mac_system.py/__random_string--crossover with--dataset/ETHPy150Open kuri65536/python-for-android/python-modules/zope/zope/interface/tests/test_interface.py/test_invariant_as_decorator