cloneContents: function () {
    // clone subtree
    return (function cloneSubtree(iterator) {
        for (var node, frag = document.createDocumentFragment(); node = iterator.next();) {
            node = node.cloneNode(!iterator.hasPartialSubtree());
            if (iterator.hasPartialSubtree()) {
                node.appendChild(cloneSubtree(iterator.getSubtreeIterator()));
            }
            frag.appendChild(node);
        }
        return frag;
    })(new RangeIterator(this));
}