/**
  * Get singleton instance
  *
  * @param object ilLuceneQueryParser
  * @return ilLuceneSearcher
  * @static
  */
 public static function getInstance(ilLuceneQueryParser $qp)
 {
     if (self::$instance) {
         return self::$instance;
     }
     return self::$instance = new ilLuceneSearcher($qp);
 }