code: public void addListener(KeyedMessage keyedMessage,
              VehicleMessage.Listener listener) {
          addListener(keyedMessage.getKey(), listener);
      }
docs: Register to receive a callback when a message with same key as the given
  KeyedMessage is received.
  
  @param keyedMessage A message with the key you want to receive updates
  for - the response to a command typically has the same key as the
  request, so you can use the outgoing message's KeyedMessage to
  register to receive a response.
  @param listener An listener instance to receive the callback.