An introduction to PyObjC describes the general method for translating Objective-C calls into Python calls, including the handling of pass-by-reference arguments and buffers.
This document describes where the PyObjC bindings for this framework are different from the general rule, such as mentioning APIs that are not supported or where the interface is different than expected.
All functions in this framework are mapped, however the unittests for this framework wrapper cause crashes in the Python interpreter.
I’m pretty sure that is due to misuse of the API, sadly enough I haven’t found good documentation or examples for the problematic functions yet. For this reason a large subset of the framework interface is not tested at the moment.