public void draw(Graphics2D g2){
        for (int i = 0; i < nodes.size(); i++){
            Node n = (Node) nodes.get(i);
            n.draw(g2);
        }
        
        for (int i = 0; i < edges.size(); i++){
            Edge e = (Edge) edges.get(i);
            e.draw(g2);
        }
        
        for (int i = 0; i < labels.size(); i++){
            PSTLabel label = (PSTLabel) labels.get(i);
            label.draw(g2);
        }
    }