@Override
  public void addListener(OnDataTaskCompletedCallback listener) {
    super.addListener(listener);

    /**
     * Check if the waitList contains items, if so invoke the new listener and clear the waitList.
     */
    if (!waitList.isEmpty()) {
      listener.onDataTaskCompleted(waitList);
      waitList.clear();
      Log.i(
          "DataProcessingManager", "addListener() - invoked the new listener with the queued data");
    }
  }
 @Override
 public void trim() {
   super.trim();
   waitList.clear();
 }