public function withGuid(string $guid): self
    {
        $this->guid        = $guid;
        $this->isPermaLink = true;
        return $this;
    }
public function withGuid(string $guid): self
    {
        $this->guid        = $guid;
        $this->isPermaLink = true;
        return $this;
    }
public function withGuid ( string $ guid ) : self { $ this -> guid = $ guid ; $ this -> isPermaLink = true ; return $ this ; }
set id of rss feed item

@param   string  $guid         the id of the item
@return  \stubbles\xml\rss\RssFeedItem
set id of rss feed item