Python 2 support – now basically all Python 2.7 syntax is supported in Python 2 mode.

That sounds excellent! I’d love to have static type checking as an extra check for my Python code, like pylint or pyflakes. But…

For code that needs to be Python 2 compatible, function type annotations are given in comments, since the function annotation syntax was introduced in Python 3.

…so now that’s three systems for declaring types: comment-based syntax for Python 2, native annotations for Python 3, and docstrings for Sphinx. I really, really wish there was some level of interop between the human- and machine-documentation systems.