Add a check method for custom type tensor (#31290)
Summary:
For backend integration, backend (e.g. Glow) needs to check the content of the tensor to determine whether it is a legit byte tensor or some special packed format. This provides a convenient interface for that.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31290
Reviewed By: jackm321, qizzzh
Differential Revision: D19069684
Pulled By: yinghai
fbshipit-source-id: 63360fa2c4d32695fe9767a40027d446d63efdd4
