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static function getDirections(){
   if(!\Bitrix\Main\Loader::includeModule('iblock') ) return;

   $rsParentSection = \Bitrix\Main\CIBlockSection::GetByID(173);
... 

$rsParentSection = CIBlockSection::GetByID(173);

   static function getDirections(){
      $tmp = array();
      $rsParentSection = CIBlockSection::GetByID(173);
      if( $arParentSection = $rsParentSection->GetNext() ){
         $arFilter = array('IBLOCK_ID' => $arParentSection['IBLOCK_ID'],'>LEFT_MARGIN' => $arParentSection['LEFT_MARGIN'],'<RIGHT_MARGIN' => $arParentSection['RIGHT_MARGIN'],'>DEPTH_LEVEL' => $arParentSection['DEPTH_LEVEL']); // выберет потомков без учета активности
         $rsSect = CIBlockSection::GetList( array('left_margin' => 'asc' ),$arFilter);
         while( $arSect = $rsSect->GetNext() ){
            // получаем подразделы
            $tmp[$arSect['ID']] = $arSect['NAME'];
         }
      }
      return $tmp;
   }

   static function getDirections(){
      $rows = array();
      $result = \Bitrix\Iblock\SectionTable::getList(array(
            'filter' => array('=IBLOCK_SECTION_ID' => 173),
      ));
      while( $row = $result->fetch() ){
         $rows[] = $row;
      }
      return $rows;
   }