/**
  * @param Webforge\Types\EnclosingType $collectionType
  * @chainable
  */
 public function setCollectionType(TraversableType $collectionType)
 {
     $this->collectionType = $collectionType;
     if ($this->itemType) {
         $this->collectionType->setType($this->itemType);
     }
     return $this;
 }