deletion problem

I have tried the human meta rig addon. Since I cannot handle this I delete the rig but I found there are lots of stuff stay in the blend file. how can i delete them ?
I want to delete all the WGT prefix objects.

If you delete, then save and close or reopen, do they stay still?

yes, they are not delete after reopen the file.

This is a truly noop question.
Finally I found they can be deleted by right clicking -> delete one by one on the panel.