Function bound 

fn bound(cert: &Cert, address: &str) -> bool

Whether a key holds address among its user IDs bound to it, as Sequoia’s policy sees them: a user ID with no binding signature of the key’s own, revoked, or bound under an algorithm the policy refuses, names nothing (review of 19 October 2026, F1: userids() alone counts every user ID, “even those without a binding signature”).