add an assertion to check the param num (#18145)
Summary:
Introduce this check to see whether it will break any existing workflow
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18145
Reviewed By: dzhulgakov
Differential Revision: D14511711
Pulled By: houseroad
fbshipit-source-id: a7bb6ac84c9133fe94d3fe2f1a8566faed14a136
