/**
  * Registers a list of columns.
  * 
  * @param DbRecord $record   Record
  * @param string[] $colPaths Column paths
  * 
  * @return DbRecordColumn[]
  */
 private function _regColumns($record, $colPaths)
 {
     $ret = [];
     foreach ($colPaths as $colPath) {
         array_push($ret, $record->regColumn($colPath));
     }
     return $ret;
 }