def get_boundary_line_vector(self, interval):
        """
        Get the polylines of the map, represented by a set of points
        """
        ret = {}
        for lane_id, data in self.blocks[-1].map_data.items():
            type = data.get("type", None)
            map_feat_id = str(lane_id)
            if MetaDriveType.is_road_line(type):
                if len(data[ScenarioDescription.POLYLINE]) <= 1:
                    continue
                line = np.asarray(data[ScenarioDescription.POLYLINE])[..., :2]
                length = get_polyline_length(line)
                resampled = resample_polyline(line, interval) if length > interval * 2 else line
                if MetaDriveType.is_broken_line(type):
                    ret[map_feat_id] = {
                        "type": MetaDriveType.LINE_BROKEN_SINGLE_YELLOW
                        if MetaDriveType.is_yellow_line(type) else MetaDriveType.LINE_BROKEN_SINGLE_WHITE,
                        "polyline": resampled
                    }
                else:
                    ret[map_feat_id] = {
                        "polyline": resampled,
                        "type": MetaDriveType.LINE_SOLID_SINGLE_YELLOW
                        if MetaDriveType.is_yellow_line(type) else MetaDriveType.LINE_SOLID_SINGLE_WHITE
                    }
            elif MetaDriveType.is_road_boundary_line(type):
                line = np.asarray(data[ScenarioDescription.POLYLINE])[..., :2]
                length = get_polyline_length(line)
                resampled = resample_polyline(line, interval) if length > interval * 2 else line
                ret[map_feat_id] = {"polyline": resampled, "type": MetaDriveType.BOUNDARY_LINE}
            elif MetaDriveType.is_lane(type):
                continue
            # else:
            # # for debug
            #     raise ValueError
        return ret

        Get the polylines of the map, represented by a set of points
        
metadrive/component/map/scenario_map.py