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 badmatch(match, badfn):
    """Make a copy of the given matcher, replacing its bad method with the given
    one.
    """
    m = copy.copy(match)
    m.bad = badfn
    return m