MPO: Fix typing that doesn't work in python 3.8. PiperOrigin-RevId: 476083485 Change-Id: I665932f10742b2f1f080f98d5e0b772bab116eb2
MPO: Fix typing that doesn't work in python 3.8.
PiperOrigin-RevId: 476083485
Change-Id: I665932f10742b2f1f080f98d5e0b772bab116eb2

deepmind/acme,deepmind/acme