Backup and restore

Hi,
So, I am working on modifying an existing (looks defunct plugin) and i am trying to implment the backup / restore functionality. Is there any good documentation for creating this functionality. what functions are expected what they are expected to do...i've looked at a few examples from other plugings but, actually documentation would be priceless.

specifically the check_backup_mods functions i am looking to see what they are actually expected to be doing.

Thanks!
Joe