Add prefix to object before spawning to avoid object registered twice…

… in engine (#659)

* Add prefix to object before spawning to avoid object registered twice in engine

* format

metadrive/manager/scenario_light_manager.py

@@ -13,6 +13,8 @@
 class ScenarioLightManager(BaseManager):
     CLEAR_LIGHTS = False
 
+    OBJECT_PREFIX = "traffic_light_"
+
     def __init__(self):
         super(ScenarioLightManager, self).__init__()
         self._scenario_id_to_obj_id = {}
@@ -41,12 +43,15 @@ def after_reset(self):
                     )
             lane_info = self.engine.current_map.road_network.graph[str(scenario_lane_id)]
             position = self._get_light_position(light_info)
-            name = scenario_lane_id if self.engine.global_config["force_reuse_object_name"] else None
+            name = self.OBJECT_PREFIX + scenario_lane_id if self.engine.global_config["force_reuse_object_name"
+                                                                                      ] else None
             traffic_light = self.spawn_object(ScenarioTrafficLight, lane=lane_info.lane, position=position, name=name)
             self._scenario_id_to_obj_id[scenario_lane_id] = traffic_light.id
             self._obj_id_to_scenario_id[traffic_light.id] = scenario_lane_id
             if self.engine.global_config["force_reuse_object_name"]:
-                assert scenario_lane_id == traffic_light.id, "Original id should be assigned to traffic lights"
+                assert self.OBJECT_PREFIX + scenario_lane_id == traffic_light.id, (
+                    "Original id should be assigned to traffic lights"
+                )
             self._lane_index_to_obj[lane_info.lane.index] = traffic_light
             status = light_info[SD.TRAFFIC_LIGHT_STATUS][self.episode_step]
             traffic_light.set_status(status)