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 __get_linearForce_title_keys(lf):
    if 'force_r' in lf:
        return ['Force r', 'Force z'], ['force_r', 'force_z']
    return ['Force x', 'Force y'], ['force_x', 'force_y']