focus with PMW

[Pete]

I am trying to determine which widget,  the focus is currently on in my
code.  When I make a call to get_focus() it gives me an instance of a
TKinter.Entry,  but I am only creating PMW widgets (which are of course
extended from TKinter).  Since I am not creating TKinter widgets
explicitly in my own code,  how can I determine which PMW widget that
specific TKinter.Entry instance belongs to?