How do I trampoline a unique_ptr reference in the smart_holder branch?

[daltairwalter]

The notes in the smart_holder branch seem to be very focused on unique_ptr, but I can't figure out how to use unique_ptr as an argument in a trampoline function. I would like to pass a reference to a unique_ptr to python. My C++ code still owns the object, but I want python to be able to access it for the duration of the python function. I can use .get(), but this loses the concept of unique_ptr and if python holds the pointer I see a crash later.

The smart_holder branch is working well for me otherwise, I have always had to hack pybind11 quite a bit for shared_ptr and shared_ptr seems to be working properly for me - also changing 9 projects over to use progressive mode only took about 20 minutes - this was a relatively painless transition.