Update src/array_api_extra/_lib/_utils/_helpers.py

Co-authored-by: Pearu Peterson <[email protected]>

Author: crusaderky

src/array_api_extra/_lib/_utils/_helpers.py

@@ -428,7 +428,7 @@ def persistent_id(self, obj: object) -> Literal[0, 1, None]:  # pyright: ignore[
             try:
                 # Note: a class that defines __slots__ without defining __getstate__
                 # cannot be pickled with __reduce__(), but can with __reduce_ex__(5)
-                _ = obj.__reduce_ex__(5)
+                _ = obj.__reduce_ex__(pickle.HIGHEST_PROTOCOL)
             except Exception:  # pylint: disable=broad-exception-caught
                 rest.append(obj)
                 return 1