public function translate($locale = null) {
        $locale = isset($locale) ? $locale : Locale\get_active_locale();

        if( in_array( $locale, Locale\get_locales() ) )
            throw new TranslatableException(
                _('Invalid locale')
            );

        $language = $this->getByLocale($locale);

        return $this->translations()
            ->where('language_id', $language->id)
            ->first();
    }