code: def test_save_extra(self):
      inp = (torch.tensor([0.1, 0.1]),)
  
      def f(x):
          return x * x + x
  
      ep = export(f, inp)
  
      buffer = io.BytesIO()
      save(ep, buffer, extra_files={"extra.txt": "moo"})
      buffer.seek(0)
      extra_files = {"extra.txt": ""}
      loaded_ep = load(buffer, extra_files=extra_files)
  
      self.assertTrue(torch.allclose(ep(*inp), loaded_ep(*inp)))
      self.assertEqual(extra_files["extra.txt"], "moo")
  
imports: import io
  import pathlib
  import tempfile
  import unittest
  import zipfile
  import torch
  import torch._dynamo
  from torch.export import export, save, load, Dim
  from torch._export.db.case import ExportCase, normalize_inputs, SupportLevel
  from torch._export.db.examples import all_examples
  from torch._export.serde.serialize import ExportedProgramDeserializer, ExportedProgramSerializer, canonicalize, deserialize, serialize, SerializeError
  from torch._subclasses.fake_tensor import FakeTensor
  from torch.fx.experimental.symbolic_shapes import is_concrete_int
  import torch.utils._pytree
  from torch.testing._internal.common_utils import instantiate_parametrized_tests, parametrize, run_tests, TestCase, TemporaryFileName, IS_FBCODE, IS_MACOS, IS_SANDCASTLE, IS_WINDOWS, find_library_location
label_desc: Use image node_id 4 for calling the TestSaveLoad obj's underlying member method code with example usage: obj.test_save_extra() and returns: unknown