pytorch

32b37ba2 - [DDP Communication Hook] Update the typing info of comm hook output as well as some docstring (#62457)

[DDP Communication Hook] Update the typing info of comm hook output as well as some docstring (#62457) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/62457 Specify `Future[torch.Tensor]` as DDP communication hook return type, which should be explicitly a single tensor. The previous API takes a list that has a single tensor. Note that now the typing info no longer accepts the internal type of `torch._C.Future`, which does not support torchscript and hence cannot support `Future[torch.Tensor]`. ghstack-source-id: 134771419 Test Plan: buck test mode/dev-nosan caffe2/test/distributed:c10d -- test_default_ddp_comm_hooks_nccl buck test mode/dev-nosan caffe2/test/distributed:c10d -- test_ddp_invalid_comm_hook_return_type Reviewed By: rohan-varma Differential Revision: D30007390 fbshipit-source-id: 246667c9b575b4c6e617b0a5b373151f1bd81e7f