def get_lane(self, index: LaneIndex) -> AbstractLane:
        """
        Get the lane geometry corresponding to a given index in the road network.

        :param index: a tuple (origin node, destination node, lane id on the road).
        :return: the corresponding lane geometry.
        """
        _from, _to, _id = index
        if _id is None and len(self.graph[_from][_to]) == 1:
            _id = 0
        return self.graph[_from][_to][_id]

        Get the lane geometry corresponding to a given index in the road network.

        :param index: a tuple (origin node, destination node, lane id on the road).
        :return: the corresponding lane geometry.
        
metadrive/component/road_network/node_road_network.py