/**
  * Get the articles.
  *
  * @param string $articleNumber Article number to filter on.
  * @return Get\ApiResponse
  */
 public function getArticles($articleNumber = null)
 {
     $requestData = new Get\RequestData();
     $requestData->setArticleNumber($articleNumber);
     $request = new Get\Request($requestData);
     return $this->sendRequest($request, Get\ApiResponse::class);
 }
 /**
  * Get one article by article number.
  *
  * @param string $articleNumber Article number of the article to get.
  * @return Article|null
  */
 public function getArticle($articleNumber)
 {
     $requestData = new Get\RequestData();
     $requestData->setArticleNumber($articleNumber);
     $request = new Get\Request($requestData);
     $request->setLimit(1);
     /** @var Get\ApiResponse $apiResponse */
     $apiResponse = $this->sendRequest($request, Get\ApiResponse::class);
     $articles = $apiResponse->getResponse()->getArticles();
     return isset($articles[0]) ? $articles[0] : null;
 }