Fix T_co import bug (#484)

* Fix T_co import bug

* Fix styling

src/lighteval/data.py

@@ -25,8 +25,15 @@
 from typing import Iterator, Tuple
 
 import torch
+from packaging import version
 from torch.utils.data import Dataset
-from torch.utils.data.distributed import DistributedSampler, T_co
+
+
+if version.parse(torch.__version__) >= version.parse("2.5.0"):
+    from torch.utils.data.distributed import DistributedSampler, _T_co
+else:
+    from torch.utils.data.distributed import DistributedSampler
+    from torch.utils.data.distributed import T_co as _T_co
 
 from lighteval.tasks.requests import (
     GreedyUntilRequest,
@@ -318,7 +325,7 @@ class GenDistributedSampler(DistributedSampler):
     as our samples are sorted by length.
     """
 
-    def __iter__(self) -> Iterator[T_co]:
+    def __iter__(self) -> Iterator[_T_co]:
         if self.shuffle:
             # deterministically shuffle based on epoch and seed
             g = torch.Generator()