convert torch.split return to list in RAFT (#7597)

Author: pmeier

torchvision/prototype/models/depth/stereo/raft_stereo.py

@@ -450,7 +450,12 @@ def forward(
             hidden_state, context = torch.split(context_outs[i], [hidden_dims[i], context_out_channels[i]], dim=1)
             hidden_states.append(torch.tanh(hidden_state))
             contexts.append(
-                torch.split(context_conv(F.relu(context)), [hidden_dims[i], hidden_dims[i], hidden_dims[i]], dim=1)
+                # mypy is technically correct here. The return type of `torch.split` was incorrectly annotated with
+                # `List[int]` although it should have been `Tuple[Tensor, ...]`. However, the latter is not supported by
+                # JIT and thus we have to keep the wrong annotation here and silence mypy.
+                torch.split(  # type: ignore[arg-type]
+                    context_conv(F.relu(context)), [hidden_dims[i], hidden_dims[i], hidden_dims[i]], dim=1
+                )
             )
 
         _, Cf, Hf, Wf = fmap1.shape