Fix indexing typing error

Author: ofsouzap

pandas/core/indexing.py

@@ -914,7 +914,7 @@ def __setitem__(self, key, value) -> None:
         indexer = self._get_setitem_indexer(key)
         self._has_valid_setitem_indexer(key)
 
-        iloc = self if self.name == "iloc" else self.obj.iloc
+        iloc: _iLocIndexer = cast("_iLocIndexer", self) if self.name == "iloc" else self.obj.iloc
         iloc._setitem_with_indexer(indexer, value, self.name)
 
     def _validate_key(self, key, axis: AxisInt) -> None: