Som problems about the messaging system

[Bob Wong]

Hello everyone,
Now I'm using python embedded module and message system trying to change the 
value of a variable. And I use the self.message_port_pub function. But the 
function requires the first one to be the output port, and the second one must 
be a pmt variable. But when I just do that convert, message pair to var will 
give me the error like: warning: Input message X is not a simple pair, 
dropping, so how can I send out the simple pair with the python module just 
like the QT GUI Toggle do? I search the Internet and get no luck. Also, I also 
can't find any document related to the self function. Where can I get the 
document related to that? In the attachment is the grc file I made. 
Thanks.

music_tx_hackrf.grc
Description: application/gnuradio-grc