positional and kwargs corner case fix in for _build_args_kwargs (pyto…

…rch#2714)

Summary:

## Context:
Setting None in positional args is colliding with the kwargs in situations when kwargs contains the argument name accepted by the method.

Eg :
```
def input_dist(ctx, id_feature_list):
    ...

// If _build_args_kwargs returns:
args = [None]
kwargs = {'id_feature_list': KJT}

input_dist(ctx, *args, **kwargs)
// extends to
input_dist(ctx, None, id_feature_list=KJT)
```

which results in "TypeError: got multiple values for argument 'id_feature_list'" because id_feature_list is provided both positionally (None) and via kwargs.

## Fix:
Ensure _build_args_kwargs does not append None to args when an argument is already correctly assigned in kwargs.

Differential Revision: D68892351

torchrec/distributed/train_pipeline/utils.py

@@ -230,7 +230,10 @@ def _build_args_kwargs(
             else:
                 args.append(arg)
         else:
-            args.append(None)
+            if arg_info.name:
+                kwargs[arg_info.name] = None
+            else:
+                args.append(None)
     return args, kwargs