DEPR: remove Index fastpath kwarg
@WillAyd are the mypy complaints actually caused by something here or just a coincidence? Doesn't make sense on first glance; just restarted let's see @simonjayhawkins any ideas whats going on with mypy here? might be relevant to this issue @jbrockmendel 

https://github.com/python/mypy/issues/1174 > @simonjayhawkins any ideas whats going on with mypy here?

we had this issue before, see https://github.com/pandas-dev/pandas/pull/29205#issuecomment-546030059

did reach an agreement whether it is a bug or expected behaviour.

the change to the function signatures has triggered this. > did reach an agreement whether it is a bug or expected behaviour.

suggestions on what to do here?  It looks like @TomAugspurger was working on making a fixture for just [Index, Series] at one point > fixture for just [Index, Series] at one point

Do you mean a TypeVar?

I don't recall the details, but I think my preference was to add `type: ignore` to the lines in the test files that were causing the (maybe buggy) inference by mypy. But I didn't really understand the issue enough to say what the expected / right behavior is. > lgtm. I see your typing TODOs, any objections to simply merging and fixing later? @simonjayhawkins

sure Thanks @jbrockmendel 