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 _rename_item_names(self, start_index):
    for index, item in enumerate(self._items[start_index:]):
      item.label.set_label(self._get_item_name(index + 1 + start_index))