public static function getInstance($x1, $y1, $x2, $y2, $id = null, $style = null)
 {
     $rect = new SVGLine('<line></line>');
     $rect->setX1($x1);
     $rect->setX2($x2);
     $rect->setY1($y1);
     $rect->setY2($y2);
     $rect->setId($id);
     $rect->setStyle($style);
     return $rect;
 }