function setAttachment(string $attachment, string $filename = '') {
        $this->attachment = $attachment;
        $this->filename = $filename;
        return $this;
    }
function setAttachment(string $attachment, string $filename = '') {
        $this->attachment = $attachment;
        $this->filename = $filename;
        return $this;
    }
function setAttachment ( string $ attachment , string $ filename = '' ) { $ this -> attachment = $ attachment ; $ this -> filename = $ filename ; return $ this ; }
Sets the attachment.
@param string  $attachment  An URL or the filepath, or the data.
@param string  $filename    The filename.
@return $this
Sets the attachment .