code: private function collectRulesFor($parentSetting, $filterSettings)
      {
          $childInformation = $this->database
              ->createQueryBuilder()
              ->select('*')
              ->from('tl_metamodel_filtersetting')
              ->where('pid=:pid')
              ->andWhere('enabled=1')
              ->orderBy('sorting', 'ASC')
              ->setParameter('pid', $parentSetting->get('id'))
              ->execute();
  
          foreach ($childInformation->fetchAll(\PDO::FETCH_ASSOC) as $item) {
              $childSetting = $this->createSetting($item, $filterSettings);
              if ($childSetting) {
                  $parentSetting->addChild($childSetting);
              }
          }
      }
docs: Fetch all child rules for the given setting.
  
  @param IWithChildren $parentSetting  The information from which to initialize the setting from.
  
  @param ICollection   $filterSettings The filter setting instance.
  
  @return void