Multi label margin loss (#50007)
Summary:
Reopen PR for https://github.com/pytorch/pytorch/pull/46975
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50007
Reviewed By: mruberry
Differential Revision: D25850808
Pulled By: ngimel
fbshipit-source-id: a232e02949182b7d3799448d24ad54a9e0bcf95c
