root.addItem(new CheckBox("item3"));
FastTree t = new FastTree();
// tree2
FastTreeItem root2 = new FastTreeItem("child root");
root2.addItem("child item0");
root2.addItem("child item1");
root2.addItem("child item2");
root2.addItem(new CheckBox("child item3"));
FastTree t2 = new FastTree();