public void uninstall(IModel model) {
   /*
    * since we do a multi install, we need to make sure we only dispose of the
    * tool once it has been removed from all
    */
   if (_installedModels.remove(model) && _installedModels.size() == 0) {
     MarkerManager.get().removeListener(_markerListener);
     if (_markerIndex != null) {
       _markerIndex.dispose();
       _markerIndex = null;
     }
   }
 }
 public void install(IModel model, Executor executor) {
   MarkerManager.get().addListener(_markerListener, executor);
   _installedModels.add(model);
 }