code: func (po *PrintOperation) PrintOperationGetError() error {
  	var err *C.GError = nil
  	C.gtk_print_operation_get_error(po.native(), &err)
  	defer C.g_error_free(err)
  	return errors.New(C.GoString((*C.char)(err.message)))
  }
docs: // GetError() is a wrapper around gtk_print_operation_get_error().