How to programmatically add members to groups

I would like to write some code that will assign members to groups, what’s the API I should use for this? Currently I doing some work in the back-end using:

import wixUsersBackend from'wix-users-backend';

But I can’t find any APIs related to groups.
Thank you.

Were you ever able to use the addMembersToGroup backend method to successfully add member to a group ? If so i would like your help on how to do that. TIA.