[GNC] Missing Documentation

[Robert Simmons]

Please correct me if I am wrong, but the Python bindings documentation is
automatically generated, right?

I looked in both master and maint, and I don't see documentation for
"Bill", but it shows up in the python bindings results from both help() and
dir(). And this object is a full object for vendor bills.

Is there a reason it was omitted from the documentation or its generation
process? If this was omitted by design, what is the thinking there?