tt.addContainerProperty("component", Component.class, "");
tt.addContainerProperty("type", String.class, "bar");
Layout l = new HorizontalLayout();
l.addComponent(new Label("bar"));
l.addComponent(new Label("bar"));
tt.addItem(new Object[] { l, "HorizontalLayout" }, 1);
l = new VerticalLayout();
l.addComponent(new Label("baz"));