def get_all_lanes(self):
        """
        This function will return all lanes in the road network
        :return: list of lanes
        """
        ret = []
        for _from, _to_dict in self.graph.items():
            for _to, lanes in _to_dict.items():
                ret += lanes
        return ret

        This function will return all lanes in the road network
        :return: list of lanes
        
metadrive/component/road_network/node_road_network.py