running commands on stop

[Jerry Dunmire]

Is there a way to run commands when the Stop button on the ToolBar is 
pressed? I am working on an activity that starts a co-process and I want 
to terminate the co-process when the activity is stopped.

Since I am new to python and sugar, any advice on how to look this 
information up would be welcome. I've been trying to look through the 
source code in git and running pydoc, but I feel like there is a better way.

Thanks,
...jerry