code: def test_regexes_with_backslashes(self):
      bad_regex = self.TEST_DIR / "bad_regex.jsonnet"
      good_regex = self.TEST_DIR / "good_regex.jsonnet"
  
      with open(bad_regex, "w") as f:
          f.write(r'{"myRegex": "a\.b"}')
  
      with open(good_regex, "w") as f:
          f.write(r'{"myRegex": "a\\.b"}')
  
      with pytest.raises(RuntimeError):
          Params.from_file(bad_regex)
  
      params = Params.from_file(good_regex)
      regex = params["myRegex"]
  
      assert re.match(regex, "a.b")
      assert not re.match(regex, "a-b")
  
      # Check roundtripping
      good_regex2 = self.TEST_DIR / "good_regex2.jsonnet"
      with open(good_regex2, "w") as f:
          f.write(json.dumps(params.as_dict()))
      params2 = Params.from_file(good_regex2)
  
      assert params.as_dict() == params2.as_dict()
  
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 9 for calling the TestParams obj's underlying member method code with example usage: obj.test_regexes_with_backslashes() without return types