protected function _parseTokens($item) {
        $results = [];
        while ($item !== null) {
            switch ($item['token']) {
                case '}':
                    return $results;

                case '{':
                    $item['children'] = $this->_parseTokens(array_shift($this->_tokens));
                    $results[] = $item;
                    break;

                default:
                    $results[] = $item;
            }

            $item = array_shift($this->_tokens);
        }
        return $results;
    }