/**
 * Retrieve object using using composite pkey values.
 * @param string $grp_uid
   @param string $usr_uid
   
 * @param      Connection $con
 * @return     GroupUser
 */
 public static function retrieveByPK($grp_uid, $usr_uid, $con = null)
 {
     if ($con === null) {
         $con = Propel::getConnection(self::DATABASE_NAME);
     }
     $criteria = new Criteria();
     $criteria->add(GroupUserPeer::GRP_UID, $grp_uid);
     $criteria->add(GroupUserPeer::USR_UID, $usr_uid);
     $v = GroupUserPeer::doSelect($criteria, $con);
     return !empty($v) ? $v[0] : null;
 }