I think I am blanking on a concept...

I want to do a query that returns all users that have a value in an
attribute. Like Login Expiration. Not everyone has one, only a subset
of my users.

So while I could query back the entire Vault, into a nodeset, and thank
to Father Ramons super cool trick, I could strip Xpath on that nodeset
something like not(attr[attr-name="Login Expiration']) which would cut
it down.

But I would rather let the query token (which is designed to query and
filter) do the work for me...

Do I skip Match attribute, and just specify an attribute to return? Or
do I specify a Match, where the attribute is named, looking for a value
of * (asterisk) or the like? (Maybe it needs to be .+ (regex version)?

I am blanking on the concept right now.