pub fn expand<I: Numeric, N: Size>(
scope: &Scope,
_n: usize,
input: &<[Vector<I, N>] as CubeType>::ExpandType,
output: &mut <[Vector<I, N>] as CubeType>::ExpandType,
n_iter: <usize as CubeType>::ExpandType,
_dtype: StorageType,
)