Restore compatibility with Python 3.8 (#1189)

* Restore compatibility with Python 3.8

Signed-off-by: Przemyslaw Tredak <ptredak@nvidia.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Signed-off-by: Przemyslaw Tredak <ptredak@nvidia.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

transformer_engine/pytorch/distributed.py

@@ -354,12 +354,8 @@ def backward(
 
         # Compute the forward pass.
         detached_inputs = detach_variable(inputs)
-        with (
-            torch.enable_grad(),
-            ctx.recompute_ctx,
-            ctx.torch_gpu_amp_ctx,
-            ctx.torch_cpu_amp_ctx,
-            activation_recompute_forward(activation_recompute=True, recompute_phase=True),
+        with torch.enable_grad(), ctx.recompute_ctx, ctx.torch_gpu_amp_ctx, ctx.torch_cpu_amp_ctx, activation_recompute_forward(
+            activation_recompute=True, recompute_phase=True
         ):
             outputs = ctx.run_function(*detached_inputs, **ctx.kwargs)
 
@@ -680,13 +676,9 @@ def checkpoint(
     torch_gpu_amp_forward_ctx, torch_cpu_amp_forward_ctx = _get_active_autocast_contexts()
 
     def recompute_fn(*args, **kwargs):
-        with (
-            torch.autograd.enable_grad(),
-            te_recompute_ctx,
-            user_recompute_ctx,
-            torch_gpu_amp_forward_ctx,
-            torch_cpu_amp_forward_ctx,
-        ):
+        with torch.autograd.enable_grad(), (
+            te_recompute_ctx
+        ), user_recompute_ctx, torch_gpu_amp_forward_ctx, torch_cpu_amp_forward_ctx:
             function(*args, **kwargs)
 
     # Initialize a new checkpoint frame for each new forward pass.