/**
  * @param graphSelectionEvent GraphSelectionEvent
  * @param cell Object
  */
 private void handleSelection(GraphSelectionEvent graphSelectionEvent, Object cell) {
   if (selected(graphSelectionEvent.getCells(), cell)) {
     if (graphSelectionEvent.isAddedCell(cell)) {
       addAll(cell);
     } else {
       removeAll(cell);
     }
   }
 }