Pimcore\Model\Document::getKey PHP Method

    public function getKey()
    {
        return $this->key;
    }

 /**
  * @param Document $doc
  * @return Document
  * @throws Model\Exception
  */
 public static function wrap(Document $doc)
 {
     if ($doc instanceof Document\Hardlink) {
         if ($sourceDoc = $doc->getSourceDocument()) {
             $destDoc = self::upperCastDocument($sourceDoc);
             $destDoc->setKey($doc->getKey());
             $destDoc->setPath($doc->getRealPath());
             $destDoc->initResource(get_class($sourceDoc));
             $destDoc->setHardLinkSource($doc);
             return $destDoc;
         }
     } else {
         $sourceClass = get_class($doc);
         $doc = self::upperCastDocument($doc);
         $doc->initResource($sourceClass);
         return $doc;
     }
     return;
 }