code: func RegisterCode128(pdf barcodePdf, code string) string {
  	bcode, err := code128.Encode(code)
  	return registerBarcode(pdf, bcode, err)
  }
docs: // RegisterCode128 registers a barcode of type Code128 to the PDF, but not to
  // the page. Use Barcode() with the return value to put the barcode on the page.