I'm uncertain about earlier/alternate versions, but the current
version of mainline pybind11_stubgen requires a number of changes in
the python binding cpp files to succeed:
__repr__ implementation added for some basic types
Added default descriptions via py::arg_v variant syntax for those
cases where a __repr__ implementation made no sense (eg, for a default
sonstructor of a complex type)
Moved class declarations to precede first use in arguments/returns
Added trailing default arguments, so that mandatory args did not
follow optional args (without resorting to kwargs trickery).
