protected function getValue($string, $domain, $locale)
    {
        if (!$domain) {
            $domain = 'default';
        }

        if (!$locale) {
            $locale = 'default';
        }

        if (!isset($this->values[$locale][$domain][$string])) {
            return $string;
        }

        return $this->values[$locale][$domain][$string];
    }