public function getNodeData($id, $required = FALSE)
    {
        $query = $this->toBase();

        $query->where($this->model->getKeyName(), '=', $id);

        $data = $query->first([$this->model->getLftName(),
            $this->model->getRgtName()]);

        if (!$data && $required) {
            throw new ModelNotFoundException;
        }

        return (array)$data;
    }