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 visitdir(self, dir):
        matched = self._matcher.match_recursive(dir)
        if matched is None:
            return True
        elif matched is True:
            return "all"
        else:
            assert matched is False
            return False