I believe this is right because the wcs order is reversed from the data order.  However, I think instead of `2-axis` everywhere, it makes a lot more sense to have a mapping of `wcsaxno = {'spectral':2, 'spatial1':1, 'spatial2': 0}` and `npaxno = {'spectral':0, 'spatial1':1, 'spatial2': 2}` at the top and invoking these