Sulu\Bundle\MediaBundle\Api\Collection::getId PHP Method

    public function getId()
    {
        return $this->entity->getId();
    }

 /**
  * @param Collection $collection
  *
  * @return Collection
  */
 protected function addPreview(Collection $collection)
 {
     return $collection->setPreview($this->getPreview($collection->getId(), $collection->getLocale()));
 }