fixed relative paths in hierarchial zarr-subgroups

apps/hiopy/configure/create_dataset.py

@@ -109,4 +109,5 @@ def add_healpix_hierarchy(
         zg = dataset.create_group(name=f"{prefix}{o}")
         add_healpix_grid(zg, o)
         if o < order:
-            zg.attrs["hiopy::parent"] = f"{dataset.basename}/{prefix}{o+1}"
+            parent_name = f"{dataset.basename}/{prefix}{o+1}" if dataset.basename is not "" else f"{prefix}{o+1}"
+            zg.attrs["hiopy::parent"] = parent_name