src/I18n/I18N.php
protected function initUrlLanguagePrefixes()
    {
        $prefixes = $this->languagePrefixes;
        $defaultLanguage = isset($prefixes['']) ? $prefixes[''] : reset($this->languages);
        $prefixes[''] = $defaultLanguage;
        foreach ($this->languages as $language) {
            if (in_array($language, $prefixes)) {
                continue;
            }
            $prefix = Reaction\Helpers\Inflector::slug($language);
            $prefixes[$prefix] = $language;
        }
        $this->languagePrefixes = $prefixes;
    }
protected function initUrlLanguagePrefixes()
    {
        $prefixes = $this->languagePrefixes;
        $defaultLanguage = isset($prefixes['']) ? $prefixes[''] : reset($this->languages);
        $prefixes[''] = $defaultLanguage;
        foreach ($this->languages as $language) {
            if (in_array($language, $prefixes)) {
                continue;
            }
            $prefix = Reaction\Helpers\Inflector::slug($language);
            $prefixes[$prefix] = $language;
        }
        $this->languagePrefixes = $prefixes;
    }
Fill url language prefixes