box.initKnownVersions(listHolder, attributeName);
    private VBox<FunctionalSet<E>> getElementsBox() {	VBox<FunctionalSet<E>> box = elementsRef.get();	if (box == null) {	    box = VBox.makeNew(true, true);	    this.elementsRef = new SoftReference<VBox<FunctionalSet<E>>>(box);	}	return box;    }