protected function getVatRatesByCountryAndDate($countryCode, $date = null)
    {
        if (empty($date)) {
            $date = $this->getInvoiceDate();
        }
        $result = $this->service->getVatInfo($countryCode, $date);
        if ($result->hasMessages()) {
            $this->result->mergeMessages($result);
        }
        $vatInfo = $result->getResponse();
        // PHP5.5: array_column($vatInfo, Tag::VatRate);
        $vatInfo = array_unique(array_map(function ($vatInfo1) {
            return $vatInfo1[Tag::VatRate];
        }, $vatInfo));
        return $vatInfo;
    }