fix: restore python 3.9 compatibility by removing | operator for unio…

…n types

src/xarray_ome_ngff/core.py

@@ -1,4 +1,6 @@
+from __future__ import annotations
 from pydantic import BaseModel
+from typing import Union
 
 import pint
 
@@ -13,5 +15,5 @@ class CoordinateAttrs(BaseModel):
     units: str | None
 
 
-JSON = dict[str, "JSON"] | list["JSON"] | str | int | float | bool | None
+JSON = Union[dict[str, "JSON"], list["JSON"], str, int, float, bool, None]
 NGFF_VERSIONS = ("0.4",)

tests/test_docs.py

@@ -1,3 +1,4 @@
+from __future__ import annotations
 import pytest
 from pytest_examples import find_examples, CodeExample, EvalExample
 

tests/test_v04.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from dataclasses import dataclass
 import zarr
 import pytest