Extend IndexType to explicitly have list[int]:

  * mypy can't infer that this type is also permitted and so it complains that Collector._reset_state's id is not compatible when used inside the function (e.g. state.empty_(id) when state is Batch)

tianshou/data/batch.py

@@ -19,7 +19,13 @@
 import torch
 
 _SingleIndexType = slice | int | EllipsisType
-IndexType = np.ndarray | _SingleIndexType | list[_SingleIndexType] | tuple[_SingleIndexType, ...]
+IndexType = (
+    np.ndarray
+    | _SingleIndexType
+    | list[_SingleIndexType]
+    | tuple[_SingleIndexType, ...]
+    | list[int]
+)
 TBatch = TypeVar("TBatch", bound="BatchProtocol")
 arr_type = torch.Tensor | np.ndarray