Sulu\Bundle\MediaBundle\Entity\CollectionType::setKey PHP Method

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

 /**
  * Create a collection type with given parameter.
  *
  * @param int $id
  * @param string $key
  * @param string $name
  *
  * @return CollectionType
  */
 private function createCollectionType($id, $key, $name)
 {
     $collectionType = new CollectionType();
     $collectionType->setId($id);
     $collectionType->setKey($key);
     $collectionType->setName($name);
     return $collectionType;
 }