crodas\TextRank\Stopword::normalize_keywords PHP Method

    public function normalize_keywords(array $keywords)
    {
        $normalized = parent::normalize_keywords($keywords);
        $callback = "stem_{$this->lang}";
        $tagger = __NAMESPACE__ . '\\POS\\' . ucfirst($this->lang) . '\\Tagger';
        if (is_callable($callback)) {
            return array_map(function ($keyword) use($callback) {
                return $callback($keyword);
            }, $normalized);
        }
        return $normalized;
    }