code: def test_sample_notebooks_are_normalized(any_nb_file):
      nb = jupytext.read(any_nb_file)
  
      changes, normalized_nb = nbformat.validator.normalize(nb)
      nbformat.validate(normalized_nb)
  
      if changes:  # pragma: no cover
          with open(any_nb_file, "w") as fp:
              jupytext.write(normalized_nb, fp)
  
          assert not changes
  
      nbformat.validate(nb)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_sample_notebooks_are_normalized(any_nb_file) without return types