Add namedtuple pytree serialization (#123648)

Summary:
Fixes pytorch/pytorch#123388 (comment)

X-link: pytorch/pytorch#123648
Approved by: https://github.com/desertfire

Reviewed By: DanilBaibak

Differential Revision: D55961061

Pulled By: angelayi

fbshipit-source-id: c34b610a6835a5f04deda92e5d8658299fb2ca3c

userbenchmark/dynamo/dynamobench/common.py

@@ -1133,7 +1133,15 @@ def load(cls, model, example_inputs, device):
                 # copy.deepcopy is required to prevent any surprising side-effect,
                 # see https://github.com/pytorch/pytorch/issues/113029
                 example_outputs = copy.deepcopy(model)(*example_args, **example_kwargs)
-            _register_dataclass_output_as_pytree(example_outputs)
+
+            if pytree._is_namedtuple_instance(example_outputs):
+                typ = type(example_outputs)
+                pytree._register_namedtuple(
+                    typ,
+                    serialized_type_name=f"{typ.__module__}.{typ.__name__}",
+                )
+            else:
+                _register_dataclass_output_as_pytree(example_outputs)
 
             gm = torch.export._trace._export(
                 model,