Support `__pos__` and `positive` (#55891)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/55604.
This PR implements `torch.Tensor.__pos__` and `torch.positive` for the compatibility with NumPy’s interface. (cc: mruberry, rgommers, emcastillo and kmaehashi)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55891
Reviewed By: H-Huang
Differential Revision: D28025928
Pulled By: mruberry
fbshipit-source-id: e43e329a802f31bf8805f6efab5c2c7ef34c88b9
