Function nest_comma_separate

pub(crate) fn nest_comma_separate<'a, F, T: 'a, I>(
    title: RcDoc<'a, ()>,
    f: F,
    v: I,
) -> RcDoc<'a, ()>
where
    F: Fn(&'a T) -> RcDoc<'a>,
    I: IntoIterator<Item = &'a T>,