public ObjectProperty<ItemSorting> itemSortingProperty() {
        if (null == itemSorting) {
            itemSorting = new ObjectPropertyBase<ItemSorting>(_itemSorting) {
                @Override protected void invalidated() { fireTileEvent(DATA_EVENT); }
                @Override public Object getBean() { return Tile.this; }
                @Override public String getName() { return "itemSorting"; }
            };
            _itemSorting = null;
        }
        return itemSorting;
    }
Defines an optional node that can be used in combination with the
CustomTileSkin.
@param GRAPHIC
src/main/java/eu/hansolo/tilesfx/Tile.java