private static function GetAchievementsIDs()
 {
     if (!self::IsLoaded()) {
         self::LoadAchievements();
     }
     if (!self::$achievement_ids) {
         self::$achievement_ids = array();
         foreach (self::$achievements_storage as $achievement) {
             self::$achievement_ids[] = $achievement['achievement'];
         }
     }
     return self::$achievement_ids;
 }