zarr 3 fixes

apps/hiopy/_zarr_utils.py

 import zarr
 
-
 def get_var_group(v):
-    root = zarr.Group(store=v.store)
-    last_slash_idx = v.name.rindex("/")
-    return root[v.name[:last_slash_idx]]
+    store = zarr.open(v.store)
+    parent_group_path = '/'.join(v.path.split('/')[:-1])
+    return store[parent_group_path]
 
 
 def get_time_axis(v):

apps/hiopy/worker.py

@@ -121,10 +121,10 @@ def main():
             # compute time start index
             t0 = (
                 np.datetime64(start_datetime())
-                - np.datetime64(var_group.time.attrs["units"][len("seconds since ") :])
-            ) / np.timedelta64(1, "s") + dt
-            t0_idx = np.searchsorted(var_group.time, t0)
-            assert var_group.time[t0_idx] == t0, "start_datetime not found in time axis"
+                - np.datetime64(var_group["time"].attrs["units"][len("seconds since ") :])
+            ) / np.timedelta64(1, "s")
+            t0_idx = np.searchsorted(var_group["time"], t0)
+            assert var_group["time"][t0_idx] == t0, "start_datetime not found in time axis"
 
             # see YAC_REDUCTION_TIME_NONE etc. (TODO: pass constants through coyote)
             time_methods2yac = {"point": 0, "sum": 1, "mean": 2, "min": 3, "max": 4}
@@ -135,9 +135,8 @@ def main():
                 src_comp, src_grid = v.attrs["hiopy::yac_source"]
             else:
                 assert "hiopy::parent" in var_group.attrs, f"No source for field {v.name} specified"
-                parent_var_path = var_group.attrs["hiopy::parent"] + "/" + src_name
-                source_var = zarr.Group(store=v.store)[parent_var_path]
-                src_name = source_var.name
+                parent_var_name = var_group.attrs["hiopy::parent"] + "/" + v.name.split("/")[-1]
+                source_var = zarr.open(store=v.store)[parent_var_name]
                 source_var_gid = grid_id(source_var)
                 src_comp = src_grid = f"{args.process_group}_{source_var_gid}"
             time_method = v.attrs.get("hiopy::time_method", "point")