Documents sub properly, adds subtract alias (#43850)
Summary:
`torch.sub` was undocumented, so this PR adds its documentation, analogous to `torch.add`'s documentation, and adds the alias `torch.subtract` for `torch.sub`, too. This alias comes from NumPy (see https://numpy.org/doc/stable/reference/generated/numpy.subtract.html?highlight=subtract#numpy.subtract)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43850
Reviewed By: ngimel
Differential Revision: D23416908
Pulled By: mruberry
fbshipit-source-id: 6c4d2ebaf6ecae91f3a6efe484ce6c4dad96f016
