That's only one of the possible uses, and I'm not even sure that it would be implemented directly. Adding keywords to indexation for custom classes is not the same as modifying the standard dict type for typing.
It doesn't have to be the standard dict type, it can be typing.Dict instead. But I understand the desire to take it one step at a time. I very much hope that this type hint syntax comes along before too much longer, though.
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Ricky.
"I've never met a Kentucky man who wasn't either thinking about going home or actually going home." - Happy Chandler