Function ranked_order 

pub fn ranked_order<C, K: Eq>(
    items: Vec<Ranked<C, K>>,
    last: Option<C>,
    cap: usize,
) -> Vec<C>

The first cap commands of items in the order the module’s docs give: groups ascending, the best value first in a group, one per key first, and last, if any, in place of the last of them. cap 0 counts as 1.