@Override public Params extract(String... path) {
        try {
            INodePrivate cloneRoot;
            try {
                r.lock();
                cloneRoot = root.clone(U.Str.join(Arrays.asList(path), "/"));
            } finally { r.unlock(); }
            return new Params(cloneRoot);

        } catch(Throwable ex) {
            throw new IllegalStateException("Failed to build clone tree: " + ex);
        }
    }