[$] Status of mypy and type checking

In his 2017 Python Language Summit session, Jukka Lehtosalo updatedattendees on the status of type checking for the language, in general, andfor the mypy static type checker.There are new features in the typing module and in mypy, as wellas work in progress and planned features for both. For a feature, typehints, that is really only around three yearsold, there has been a lot of progress made-but, of course, there isstill more to come.