code: def test_get_directory_size(self):
      self.assertEqual(file_util.get_directory_size("the_dir"), 42 * 5)
  
imports: import errno
  import os
  import unittest
  from unittest.mock import MagicMock, mock_open, patch
  import pytest
  from streamlit import file_util, util
label_desc: Use image node_id 10 for calling the FileUtilTest obj's underlying member method code with example usage: obj.test_get_directory_size() without return types