/**
  * @param mixed $obj
  * @param string $alias
  *
  * @return bool
  */
 public function addMany(&$obj, $alias = '')
 {
     $added = false;
     if (is_array($obj)) {
         /** @var xPDOObject $o */
         foreach ($obj as $o) {
             if (is_object($o)) {
                 $o->set('class', $this->class_key);
                 $added = parent::addMany($obj, $alias);
             }
         }
         return $added;
     } else {
         return parent::addMany($obj, $alias);
     }
 }