fix: pooling requires HEALPix in nested ordering

Also highlight the number of neighbors as a parameter.
Fixes omission from fixing #7

deepsphere/utils/laplacian_funcs.py

@@ -100,7 +100,7 @@ def get_healpix_laplacians(nodes, depth, laplacian_type):
     for i in range(depth):
         pixel_num = nodes
         subdivisions = int(healpix_resolution_calculator(pixel_num)/2**i)
-        G = SphereHealpix(subdivisions)
+        G = SphereHealpix(subdivisions, nest=True, k=20)
         G.compute_laplacian(laplacian_type)
         laplacian = prepare_laplacian(G.L)
         laps.append(laplacian)