Michael, You’re missing a lot of concepts here. I think the Tour might help you http://tour.dgraph.io
All piece of text inserted within the parameters of a func will be considered as variable.
The concept here is that you are mixing eq with uid functions. They are different things. You will never find the UID of a Bill within the predicate Bill. For this is in the “predicate” UID.
The uid_in proposal is to locate a relation ahead. So you need a reference, so in ROOT it’s forbidden. Because you first use the uid function to later use uid_in. But such use would be useless, too. Or just used to “check”.
The concept of uid_in is “Check if this node is related to this other node”. Use it in Root is illogical, as it does not have the “this” referential.
Maybe this query below will help.
(Please note that in this case you will need to billItems as “@Reverse”)
Whereas “0xa” belongs to a Parent Node.
{
search(func: has(billItems)) @filter(uid_in(~billItems, "0xa" ))
{
uid
expand(_all_){ expand(_all_) }
}
}