/**
  * @param  LinkRelation $relation
  * @return null|string
  */
 public function getLinkUrl(LinkRelation $relation)
 {
     $links = $this->getLinks();
     foreach ($links as $link) {
         if ($link['relation'] == $relation->toNative()) {
             return $link['uri'];
         }
     }
     return null;
 }
 /**
  * @return null|string
  */
 public function getEventUrl()
 {
     $alternate = $this->getLinkUrl(LinkRelation::ALTERNATE());
     return $alternate;
 }