code: public void addListener(KeyMatcher matcher, VehicleMessage.Listener listener) {
          Log.i(TAG, "Adding listener " + listener + " to " + matcher);
          mNotifier.register(matcher, listener);
      }
docs: Register to receive a callback when a message with key matching the given
  KeyMatcher is received.
  
  This function can be used to set up a wildcard listener, or one that
  receives a wider range of responses than just a 1 to 1 match of keys.
  
  @param matcher A KeyMatcher implement the desired filtering logic.
  @param listener An listener instance to receive the callback.