Function rang_after 

fn rang_after<'a>(
    calls: &'a [Held],
    group: &[&Held],
    date: Date,
    l: &Lister<'_>,
) -> Option<&'a Held>

The first call that rang from the same number after the last of group, the same day, on any phone: none for a hidden number (two hidden calls cannot be told apart).