Function doubts_unread_at 

pub fn doubts_unread_at(
    due: i64,
    waking: i64,
    now: i64,
    record_lost: Option<i64>,
    peers: &[Peer],
    since: i64,
    heard: &BTreeSet<String>,
) -> Vec<Doubt>

doubts_unread for a dose that waited for waking (doubts_at).