let pool = Pool::<Vec<u8>>::new(
            || Vec::new(),
            |v| v.clear(),
        );
        let mut item = pool.get();

        item.push(1);
        item.push(2);
        item.push(3);

        drop(item);

        // item's memory can now be reused

        let mut item = pool.get();

        item.push(1);
        item.push(2);
        item.push(3);