[optparse] Change Uses of List[] to Sequence[] in argument positions. (#1179)
[optparse] Change Uses of List[] to Sequence[] in argument positions. (#1179)

* Change Uses of List[] to Sequence[] in argument positions.

One of these (parse_args()) broke in real-world code, because the
expected type was List[Union[str, bytes]] but the actual type was
List[str] (because List is invariant).  That is ridiculous, so I
changed the accepted type to Sequence[_Text] which is covariant.  Then
I found a few other methods/functions that probably should also be
changed to Sequence, but I'm less certain of those.  I'm not at all
sure about the instance/class attributes, so I left those alone
(though I suspect those might also have to switch).

* Fixes suggested by code review

- Changed Sequence[Option] to Iterable[Option] everywhere
- Changed _process_args to plain List

euresti/typeshed,azag0/typeshed,li-dan/typeshed