How to differentiate between local referenced 'uses' statements and foreign referenced one

[noviceAnkit]

a.yang

module a {
import b {prefix b}
container x {
leaf y {
}
uses b:z-top;
}
}

b.yang

module b {
leaf z{}
}

I am working with a.yang(Generating xpath without expanding foreign 'uses' statement), how can I differentiate between the local referenced and foreign referenced 'uses' statement, like in above example, I don't want to keep xpath expanded from "uses b" because it is not locally defined and defined in some other yang file.