How should the type of message be determined?

Hi,

Thank you all in advance, here is a message handler:

def msgHandler(self, msg):

        try:    

            newVal = pmt.to_python(pmt.cdr(msg))

            imageFile=newVal

            if type(newVal) == str:

                if not os.path.isfile(imageFile):

                    print("[GrGraphicsItem] ERROR: Unable to find file " + imageFile)

                    return

                

                try:

                    self.pixmap = QPixmap(imageFile)

                    self.imageFile = imageFile

                except OSError as e:

                    print("[GrGraphicsItem] ERROR: " + e.strerror)

                    return

                

                self.updateGraphic()

            else:

                print("[GrGraphicsItem] Error: Value received was not an int or a bool: %s" % str(e))

                

        except Exception as e:

            print("[GrGraphicsItem] Error with message conversion: %s" % str(e))

What type of message should I give this message handler?I wrote a message:

 self.message_port_pub(pmt.intern('Output'),pmt.cons(pmt.to_pmt(1),pmt.intern('/home/program/image/1.png')))

After testing with the "message debug" module, it can be printed out on the terminal (1. /Home/program/image/1.png), indicating that the message is indeed generated, but an error occurs when I send this message to the message handler ：EEROR:Unable to find file

Through the code,I used the message mechanism for the first time, I know where the problem is probably, but I don't know how to modify it

sincere regards，

linge93