public function getNaturalLanguages(bool $force = false) : CNabuLanguageList
    {
        $nb_natural = new CNabuLanguageList();
        $this->getLanguages($force)->iterate(function ($key, CNabuLanguage $nb_language) use ($nb_natural) {
            if ($nb_language->isNaturalLanguage()) {
                $nb_natural->addItem($nb_language);
            }
            return true;
        });

        return $nb_natural;
    }