GetClassOfFunc causes fatal error with extension modules

I'm attempting to use PySide2 with our application that has an embedded python interpreter.

Everything works fine, unless `inspect.signature` is called with any of our local builtin functions.

When that happens I get a fatal error from `GetClassOfFunc` this happens 100% of the time once I have loaded PySide2, but the default `inspect.signature` does not exhibit this behavior.

I'm guessing this is because the function is not a direct subclass of `builtin_function_or_method` but instead our binding generation code creates an intermediate subclass that our generated functions inherit from.

Is there anyway I can fix this short of extending shiboken2 to know about our crazy stuff? Like maybe disable signature monkeypatching that it does?