code: def test_replace_none(self):
      params = Params(
          {"a": "None", "b": [1.0, "None", 2], "c": {"d": "None"}}
      )
      assert params["a"] is None
      assert params["b"][1] is None
      assert params["c"]["d"] is None
  
imports: import json
  import os
  import re
  from collections import OrderedDict
  import pytest
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.params import infer_and_cast, Params, remove_keys_from_params, with_overrides
  from allennlp.common.testing import AllenNlpTestCase
label_desc: Use image node_id 2 for calling the TestParams obj's underlying member method code with example usage: obj.test_replace_none() without return types