docs: public void addTrackPositionListener(int player, TrackPositionListener listener) {
          listenerPlayerNumbers.put(listener, player);
          TrackPositionUpdate currentPosition = positions.get(player);
          if (currentPosition !=  null) {
              listener.movementChanged(currentPosition);
              trackPositionListeners.put(listener, currentPosition);
          } else {
              trackPositionListeners.put(listener, NO_INFORMATION);
          }
      }