Type clients as async context managers
Type clients as async context managers

Reviewed By: yfeldblum

Differential Revision: D15063940

fbshipit-source-id: 9349c63ba21f7f5361712ffe7c221205a4fae764

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift