code: protected function createLabel($content, $type, $format, $size)
      {
          $label = new OrderShipmentLabel(); // TODO use SaleFactory ?
          $label
              ->setContent($content)
              ->setType($type)
              ->setFormat($format)
              ->setSize($size);
  
          return $label;
      }
docs: Creates the shipment label.
  
  @param string $content
  @param string $type
  @param string $format
  @param string $size
  
  @return OrderShipmentLabel