I think he's talking about PEP 0484. As I understand it they go into separate files and there is a gradual typing system. The inspiration came from mypy http://

I think he's talking about PEP 0484. As I understand it they go into separate files and there is a gradual typing system. The inspiration came from mypy http://mypy-lang.org/ http://mypy-lang.org/ and the point is mainly for IDEs and convenience in development currently, though they could be used for optimizations in implementations other than the reference interpreter.