def assert_inequivalent(o1, o2):
    '''Asserts that o1 and o2 are distinct and inequivalent objects
    '''
    if not (isinstance(o1, type) and isinstance(o2, type)):
        assert o1 is not o2
    assert not o1 == o2 and o1 != o2
    assert not o2 == o1 and o2 != o1