pytorch

61d88cdd - use `const auto&` as type for grad alias (#63949)

use `const auto&` as type for grad alias (#63949) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/63949 This is an extension of the discussion in https://github.com/pytorch/pytorch/pull/63040#discussion_r687793027. Test Plan: Imported from OSS Reviewed By: albanD Differential Revision: D30546789 Pulled By: dagitses fbshipit-source-id: 3046aff4f129d5492d73dfb67717a824e16ffee8