class_docstr: OSS Filesystem Tests
code: def test_list_directory(self):
      dir_path = file_io.join(self._base_dir, "test_dir")
      gfile.MkDir(dir_path)
      files = ["file1.txt", "file2.txt", "file3.txt"]
      for name in files:
          file_path = file_io.join(str(dir_path), name)
          with gfile.Open(file_path, mode="w") as f:
              f.write("testing")
      subdir_path = file_io.join(str(dir_path), "sub_dir")
      gfile.MkDir(subdir_path)
      subdir_file_path = file_io.join(str(subdir_path), "file4.txt")
      with gfile.Open(subdir_file_path, mode="w") as f:
          f.write("testing")
      dir_list = gfile.ListDirectory(dir_path)
      self.assertItemsEqual(files + ["sub_dir"], dir_list)
  
imports: import os
  import unittest
  from tensorflow.python.framework import errors
  from tensorflow.python.lib.io import file_io
  from tensorflow.python.platform import test
  from tensorflow.python.platform import gfile
  import tensorflow
  import tensorflow_io
label_desc: Use image node_id 25 for calling the OSSFSTest obj's underlying member method code with example usage: obj.test_list_directory() without return types