pub trait LastInFirstOutQueue<B: LastInFirstOutBucket>: Queue<B> {
fn push(&mut self, item: B::Item, priority: usize) { ... }
fn pop(&mut self, priority: usize) -> Option<B::Item> { ... }
fn pop_min(&mut self) -> Option<B::Item> { ... }
fn pop_max(&mut self) -> Option<B::Item> { ... }
}