[web2py] how to access auth.is_logged_in() from modules?

[weheh]

I'm finally migrating many, possibly all model functions to modules,
where they belong. But one of my functions tests auth.is_logged_in(),
which can not be found from within modules. Nor is it a
current.<whatever>.<whatever>. I've done a bit of digging but haven't
found the answer, yet. If someone knows how to do it, I'd appreciate a
pointer. Thanks.