private function getSignResponse($signRequest)
    {
        $apiKey = $this->configHelper->getApiKey();

        //Request Data
        $requestData = $this->dataObjectFactory->create();
        $requestData->setApiData($signRequest);
        $requestData->setDynamicApiUrl(ApiHelper::API_SIGN);
        $requestData->setApiKey($apiKey);

        $request = $this->apiHelper->buildRequest($requestData);
        try {
            $result = $this->apiHelper->sendRequest($request);
        } catch (\Exception $e) {
            return null;
        }
        return $result;
    }