Function coarsen 

pub fn coarsen(
    a: &NdArrowArray,
    windows: &[(&str, usize)],
    op: Reduction,
    boundary: CoarsenBoundary,
) -> Result<NdArrowArray>

Reduce non-overlapping blocks, like xarray.DataArray.coarsen.

Each (dim, window) pair splits dim into blocks of window positions. The split itself is a reshape without a copy.