/**
  * @param  GuzzleHttp\Psr7\Response $response
  * @return array
  */
 private function convertResponse($response)
 {
     $responseHeader = $response->getHeaderLine('content-type');
     if (false == preg_match('/application\\/json/', $responseHeader)) {
         throw new ResponseFormatException();
     }
     return json_decode($response->getBody(), true);
 }