code: func RegisterCode39(pdf barcodePdf, code string, includeChecksum, fullASCIIMode bool) string {
  	bcode, err := code39.Encode(code, includeChecksum, fullASCIIMode)
  	return registerBarcode(pdf, bcode, err)
  }
docs: // RegisterCode39 registers a barcode of type Code39 to the PDF, but not to
  // the page. Use Barcode() with the return value to put the barcode on the page.
  //
  // includeChecksum and fullASCIIMode are inherited from code39.Encode().