class LevelNode {

    void add(List<String> levels, T leafValue, int depth) {
        String[] levelsArray = levels.toArray(new String[levels.size()]);
        add(levelsArray, leafValue, depth);
    }

    public  LevelNode(LevelIndex<T> index);
    public  LevelNode(String level, LevelNode<T> parent, LevelIndex<T> index);

}