private function getStyle(array $token, array $previous): string
    {
        if (!empty($previous)) {
            foreach ($this->style as $style => $tokens) {
                if (in_array($previous[1] . $token[0], $tokens)) {
                    return $style;
                }
            }
        }

        foreach ($this->style as $style => $tokens) {
            if (in_array($token[0], $tokens)) {
                return $style;
            }
        }

        return '';
    }