public function countries(array $countryCodes = null): array
    {
        if (!Configure::read('countries')) {
            Configure::load('CkTools.countries');
        }
        if ($countryCodes) {
            $countries = Configure::read('countries');
            $subset = [];
            foreach ($countryCodes as $countryCode) {
                $subset[$countryCode] = $countries[$countryCode] ?? $countryCode;
            }

            return $subset;
        }

        return Configure::read('countries');
    }