@Override
 public boolean addNode(INode newNode, Point2D p) {
   INode foundNode = findNode(p);
   if (foundNode == null
       && (newNode.getClass().isAssignableFrom(ActivationBarNode.class)
           || newNode.getClass().isAssignableFrom(EndLifeNode.class))) {
     return false;
   }
   return super.addNode(newNode, p);
 }