/**
  * Get completion for user
  * 
  * @param int $a_user_id
  * @param int $a_object_id
  * @return string datetime 
  */
 protected function getUserCompletionDate($a_user_id, $a_object_id = null)
 {
     if (!$a_object_id) {
         $a_object_id = $this->object->getId();
     }
     include_once "Services/Tracking/classes/class.ilLPStatus.php";
     return ilLPStatus::_lookupStatusChanged($a_object_id, $a_user_id);
 }