public void deleteNode(Node n){
  Assert.check(nodes.contains(n));
  nodes.remove(n);
  notifyUpdate(n,null);
}

public void deleteNode ( Node n ) { Assert . check ( nodes . contains ( n ) ) ; nodes . remove ( n ) ; notifyUpdate ( n , null ) ; }
delete a node from the graph . this update the underlying structure of the graph ( including dependencies ) via listeners updates .
