Dealing with Google's version of IMAP, CalDAV and CardDAV is with the standard that everyone else follows. Every single program (mbsync, offlineimap, vdirsyncer) needs a special section on how to configure for Google alone. It causes a lot of heartache when you try to migrate.
class GoogleContactsStorage(dav.CardDAVStorage):
on https://github.com/pimutils/vdirsyncer/blob/master/vdirsynce...