def __repr__(self):
        return "<NamedRequirements({}{})>".format(
            self.name,
            ", filename='{}'".format(self.filename.name) if self.filename
            else "")
def _on_drag_data_received(self, dragged_item_index_str, destination_item):
    dragged_item = self._items[int(dragged_item_index_str)]
    self.reorder_item(dragged_item, self._get_item_position(destination_item))