code: def test_walk_missing(tmp_dir, dvc):
      fs = DataFileSystem(index=dvc.index.data["repo"])
  
      for _ in fs.walk("dir"):
          pass
  
imports: import posixpath
  import shutil
  import pytest
  import dvc_data
  from dvc.fs import localfs
  from dvc.fs.data import DataFileSystem
  from dvc.utils.fs import remove
  from dvc_data.hashfile.build import build
  from dvc_data.hashfile.hash_info import HashInfo
label_desc: Use image node_id 12 for calling a global function with example usage: test_walk_missing(tmp_dir, dvc) without return types