def serialized(self):
        to_ret = {}
        for group, requirements in self.items():
            to_ret[group] = [str(requirement) for requirement in requirements]
        return to_ret
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)