code: def test_multi_level_nested(self):
      ori_in = OrderedDict(
          {
              "a": {
                  "b": {
                      "c": {
                          "d": 1,
                      },
                  },
              },
              "b": {
                  "c": {
                      "d": 2,
                  },
              },
              "c": {
                  "d": 3,
              },
              "e": 4,
          }
      )
      in_ = copy.deepcopy(ori_in)
      result = flatten_dict(in_)
      assert in_ == ori_in
      assert result == {"a/b/c/d": 1, "b/c/d": 2, "c/d": 3, "e": 4}
  
imports: import copy
  from collections import OrderedDict
  import pytest
  import sys
  import unittest
  from unittest.mock import patch
  from ray.tune.utils.util import wait_for_gpu
  from ray.tune.utils.util import flatten_dict, unflatten_dict, unflatten_list_dict
label_desc: Use image node_id 3 for calling the FlattenDictTest obj's underlying member method code with example usage: obj.test_multi_level_nested() without return types