public function removeDuplicateEmptyLines()
    {
        $output = [];
        $c = 0;
        foreach( $this->lines as $key => $line ) {
            if( strlen(rtrim($line)) === 0 ) {
                $c++;
                if( $c === 1 ) {
                    $output[] = $line;
                }
            } else {
                $c = 0;
                $output[] = $line;
            }
        }
        $this->lines = $output;
        return $this;
    }