def test_add_already_added(self):
        prio_set_list = event._PrioritizedSetList()
        obj = object()
        prio_set_list.add(0, obj)

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(0, obj)
        excinfo.match(r"has already been added")

        with pytest.raises(ValueError) as excinfo:
            prio_set_list.add(1, obj)
        excinfo.match(r"has already been added")
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))