Hello. I have BeanTreeView, and some nodes in it. Every node has constructor

public class ProjectNode extends AbstractNode {

public ProjectNode(MainProject obj, DiagramsChildren childrens) {
    super (new ProjectsChildren(), Lookups.singleton(obj));
    setDisplayName ( obj.getName());

}

I set Rootnode as a root for tree in ExplorerTopComponent as this:

private final ExplorerManager mgr = new ExplorerManager();
    public ExplorerTopComponent(){
    associateLookup (ExplorerUtils.createLookup(mgr, getActionMap()));

    mgr.setRootContext(new RootNode());
}

And now, how I can get MainProject obj from some node? I need to get it in another class.