def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def test_strictly_between():
    """Greater than y and less than z."""
    p = are.strictly_between(2, 4)
    ps = [p(x) for x in range(1, 6)]
    assert ps == [False, False, True, False, False]