fix tuple subscription

usp/objects/sitemap.py

@@ -13,7 +13,7 @@
 import os
 import pickle
 import tempfile
-from typing import List, Iterator
+from typing import List, Iterator, Tuple
 
 from .page import SitemapPage
 
@@ -249,7 +249,7 @@ def __eq__(self, other) -> bool:
     def __repr__(self):
         return f"{self.__class__.__name__}(url={self.url}, pages={self.pages})"
 
-    def __getstate__(self) -> tuple[None, dict]:
+    def __getstate__(self) -> Tuple[None, dict]:
         # Load slots of this class and its parents (mangling if appropriate)
         obj_slots = {slot: getattr(self, slot) for slot in _all_slots(self.__class__)}
         # Replace temp file path with actual content