API Notes: Message framework
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.
The PyObjC bindings for the Message framework are complete.
This framework is only available for 32-bit code, and was removed in Mac OS X 10.9.