This makes the type mapping available for all files in this directory (or sub-directories).
What do you think?
I don't think this should be a language feature. _Maybe_ it can be some kind of an agreed format between IDEs.
But in any case I would first discuss this on PyCharm and VScode (IntelliSense?) trackers.
Also I don't think it is a good fit for mypy (and probably other type checkers, but better ask pytype and pyre devs).
I would rather expect that IDEs auto-add annotations using some guided heuristics, and then type checkers can verify them.