code: public function findOne($productId)
      {
          $result = $this->client->request('GET', 'items/' . $productId, [
              'lang' => $this->languageHelper->getLanguagesQueryString(),
              'with' => implode(',', self::$includes),
          ]);
  
          if (empty($result)) {
              return $result;
          }
  
          $result['variations'] = $this->itemsVariationsApi->findBy([
              'itemId' => $result['id'],
              'plentyId' => implode(',', $this->variationHelper->getMappedPlentyClientIds()),
          ]);
  
          return $result;
      }
docs: @param int $productId
  
  @return array