Only label as tuple

Author: mroeschke

pandas/core/indexes/multi.py

@@ -840,7 +840,7 @@ def size(self) -> int:
     # Levels Methods
 
     @cache_readonly
-    def levels(self) -> tuple[Index, ...]:
+    def levels(self) -> tuple:
         # Use cache_readonly to ensure that self.get_locs doesn't repeatedly
         # create new IndexEngine
         # https://github.com/pandas-dev/pandas/issues/31648