[typing] Use typing_extensions.Self

Typing.Self was introduced in Python 3.11 so we cannot use it in the
3.10 pipeline.

src/ptbench/config/data/tbx11k/datamodule.py

@@ -9,6 +9,7 @@ import os
 import typing
 
 import PIL.Image
+import typing_extensions
 
 from torch.utils.data._utils.collate import default_collate_fn_map
 from torchvision.transforms.functional import to_tensor
@@ -63,7 +64,7 @@ class BoundingBox:
     def ymax(self) -> int:
         return self.ymin + self.height - 1
 
-    def intersection(self, other: typing.Self) -> int:
+    def intersection(self, other: typing_extensions.Self) -> int:
         """Computes the area intersection between bounding boxes.
 
         Notice that screen geometry dictates is slightly different from