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 _patsplit(pattern, default):
    """Split a string into the optional pattern kind prefix and the actual
    pattern."""
    if ":" in pattern:
        kind, pat = pattern.split(":", 1)
        if kind in allpatternkinds:
            return kind, pat
    return default, pattern