/**
  * Adds product variant to document.
  *
  * @param ProductDocument $document
  * @param Article         $variant
  */
 protected function modifyVariant($document, $variant)
 {
     $variantObject = new VariantObject();
     $variantObject->setId($variant->getId());
     $variantObject->setActive($variant->isActive());
     $variantObject->setSku($variant->getArtNum());
     $variantObject->setTitle($variant->getTitle());
     $variantObject->setDescription($variant->getShortDesc());
     $variantObject->setPrice($variant->getPrice());
     $variantObject->setOldPrice($variant->getTPrice());
     $variantObject->setStock($variant->getStock());
     $variantObject->setAttributes($this->attrToDocService->transform($variant->getAttributes()));
     $this->extractExtensionData($variant, $variantObject);
     $document->addVariant($variantObject);
 }