public function addFlag($flag)
    {
        
        $currentAnnotations = $this->getAnnotations();
        if (!isset($currentAnnotations[self::FLAGS])){
            $currentAnnotations[self::FLAGS] = $flag;
        }
        else if (!(mb_strpos($currentAnnotations[self::FLAGS], $flag, 0, TAO_DEFAULT_ENCODING) !== false)){
            $currentAnnotations[self::FLAGS] .= " ${flag}";
        }
    
        $this->setAnnotations($currentAnnotations);
        
    }