/**
  * Return parent model.
  *
  * @throws ParentModelNotFoundException
  * @return ElasticsearchModel
  */
 public function getOrFail()
 {
     $model = $this->get();
     if (is_null($model)) {
         throw new ParentModelNotFoundException($this->parentClass, $this->child->getParentId());
     }
     return $model;
 }