[fix] Fix a mypy issue

Author: nabenabe0928

autoPyTorch/datasets/base_dataset.py

@@ -234,7 +234,7 @@ def get_splits_from_resampling_strategy(self) -> List[Tuple[List[int], List[int]
         self._check_resampling_strategy_args()
 
         labels_to_stratify = self.train_tensors[-1] if self.is_stratify else None
-        kwargs = {}
+        kwargs: Dict[str, Any] = {}
         kwargs.update(
             random_state=self.random_state,
             shuffle=self.shuffle_split,