code: public function findByParent($parentId, $siteId)
      {
          $qa = $this->createAggregationQueryBuilderWithSiteId($siteId);
          $qa->match(array('parentId' => $parentId));
  
          return $this->hydrateAggregateQuery($qa);
      }
docs: @param string $parentId
  @param string $siteId
  
  @throws \Exception
  
  @return mixed