Embedding python cannot return the python derived class

Hi, I followed the example of embedding the Widget Class in python:
https://github.com/pybind/pybind11/blob/master/tests/test_embed/test_interpreter.cpp

I am using the same code inside a class that I created. I am trying to make the python class derivedWidget a class member or be able to return it and pass it between class members.

I am getting the error that I cannot allocate an object of abstract type.

How can py_widget or cpp_widget be a returned type?
How can py_widget or cpp_widget be declared a global variable?
How can py_widget or cpp_widget be declared a variable of a new class?

py::module py_widget = module.attr("DerivedWidget")("The question");
auto message = py_widget.attr("the_message");
const Widget &cpp_widget = py_widget.cast<const Widget &>();

Thank you.

Start with tests/test_embed/test_interpreter.cpp, the embedding example referenced in the issue, and compare it with the class-member use case described here. Determine whether the reported abstract-type error is an unsupported usage or a pybind11 defect; done requires a confirmed supported approach or a narrowly reproducible issue suitable for a separate fix.