static function fetchList($mementoKey, $asObject = true)
 {
     if (is_array($mementoKey)) {
         $mementoKey = eZOperationMemento::createKey($mementoKey);
     }
     return eZPersistentObject::fetchObjectList(eZOperationMemento::definition(), null, array('memento_key' => $mementoKey, 'main' => 0), null, null, $asObject);
 }