public function getNgAchievementLevel($con = null)
 {
     include_once 'lib/model/om/BaseNgAchievementLevelPeer.php';
     if ($this->aNgAchievementLevel === null && $this->ng_achievement_level_id !== null) {
         $this->aNgAchievementLevel = NgAchievementLevelPeer::retrieveByPK($this->ng_achievement_level_id, $con);
     }
     return $this->aNgAchievementLevel;
 }