Is there a way to handle forward declaration in pybind11?

[MartinBubel]

I am trying to write python bindings for a library that makes frequent use of forward declarations. Unfortunately, I could not yet find a way to get my pybind11 bindings to compile. I always get a large error message(s) containing error: invalid use of incomplete type ... and note: forward delcaration of class ....

I would be super greateful if anybody can help me on this issue. I attached a minimum example to reproduce the errors I am getting.
pybind11fwddclrtn.tar.gz