def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def test_below():
    """Less than y."""
    p = are.not_below(4)
    ps = [p(x) for x in range(1, 6)]
    assert ps == [False, False, False, True, True]