Use type hints whenever possible
Since we are using python 3, we can start taking advantage of type hints wherever possible.
we should probably do this in pyro too
@neerajprad @jpchen Could I work on this issue?
@akihironitta - The codebase and number of contributors to numpyro core is small enough that this is low priority for us at the moment. When I created the issue, I was thinking that we could do this in a piecemeal fashion as we were refactoring the codebase. If you are interested, my suggestion would be to start with one of the other tasks and refactor to use type hints on the internal code that your PR touches.