fn main() {
    let y = vec![
        vec![1, 2, 3, 4],
        vec![5, 6, 7, 8],
        vec![9, 10, 11, 12],
        vec![13, 14, 15, 16]
    ];

    eggsy(y);
}

fn eggsy<'a, T: AsRef<[impl AsRef<[usize]> + 'a]> + 'a>(x: T) -> &'a [&'a [usize]]{
    let as_slice :&[&[usize]] = x.as_ref();
    as_slice
    }