code: public synchronized TaskManagerMetricStore getTaskManagerMetricStore(String tmID) {
  		return tmID == null ? null : TaskManagerMetricStore.unmodifiable(taskManagers.get(tmID));
  	}
docs: Returns the {@link TaskManagerMetricStore} for the given taskmanager ID.
  
  @param tmID taskmanager ID
  @return TaskManagerMetricStore for the given ID, or null if no store for the given argument exists