Function reduce_axis 

pub fn reduce_axis<T: Copy + MaybeSendSync, Op: ElementOp<T>, M, R, U>(
    src: &StridedView<'_, T, Op>,
    axis: usize,
    map_fn: M,
    reduce_fn: R,
    init: U,
) -> Result<StridedArray<U>>
where
    M: Fn(T) -> U + MaybeSync,
    R: Fn(U, U) -> U + MaybeSync,
    U: Clone + MaybeSendSync,

Reduce along a single axis, returning a new StridedArray.