code: public function get()
      {
          $child = $this->childClassName;
          $query = new QueryBuilder();
          $query->filter(new ParentFilter($this->parent->getId()));
          $collection = $child::search($query);
          $collection->each(function (ElasticsearchModel $model) {
              $model->setParent($this->parent);
          });
          return $collection;
      }
docs: Find all children.
  
  @return ElasticsearchCollection|ElasticsearchModel[]