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 _setup_drag(self, item):
    self._drag_and_drop_context.setup_drag(
      # Using the entire item allows dragging only by the label rather than the
      # widget itself. This avoids problems with widgets such as spin buttons
      # that do not behave correctly when reordering and also avoids accidental
      # clicking and modifying the widget by the user.
      item.widget,
      self._get_drag_data,
      self._on_drag_data_received,
      [item],
      [item],
      self)