Function for_each_patch_row 

pub(super) fn for_each_patch_row(
    vdims: [usize; 3],
    patch: [usize; 3],
    origin: [usize; 3],
    f: impl FnMut(usize, usize),
)

Visit the rows of a patch at origin inside a volume: f(volume_row_start, patch_row_start).