def _get_bounding_box(self):
        """
       By using this bounding box, the edge length of x, y direction and the center of this road network can be
       easily calculated.
       :return: minimum x value, maximum x value, minimum y value, maximum y value
       """
        lanes = []
        for id, lane_info, in self.graph.items():
            lanes.append(lane_info.lane)
        res_x_max, res_x_min, res_y_max, res_y_min = get_boxes_bounding_box([get_lanes_bounding_box(lanes)])
        return res_x_min, res_x_max, res_y_min, res_y_max

       By using this bounding box, the edge length of x, y direction and the center of this road network can be
       easily calculated.
       :return: minimum x value, maximum x value, minimum y value, maximum y value
       
metadrive/component/road_network/edge_road_network.py