invokePreprocess example

public function analyze(string $text, ?string $langcode = NULL): string {
    // Decode entities to UTF-8.     $text = Html::decodeEntities($text);

    // Lowercase.     $text = mb_strtolower($text);

    // Remove diacritics.     $text = $this->transliteration->removeDiacritics($text);

    // Call an external processor for word handling.     $this->invokePreprocess($text, $langcode);

    // Simple CJK handling.     if ($this->configFactory->get('search.settings')->get('index.overlap_cjk')) {
      $text = preg_replace_callback('/[' . self::PREG_CLASS_CJK . ']+/u', [$this, 'expandCjk'], $text);
    }

    // To improve searching for numerical data such as dates, IP addresses     // or version numbers, we consider a group of numerical characters     // separated only by punctuation characters to be one piece.     // This also means that searching for e.g. '20/03/1984' also returns     // results with '20-03-1984' in them.