code: def test_TransformObservationFeatures(self) -> None:
      observation_features = [
          ObservationFeatures(parameters={"a": 2.2, "b": "b", "c": "a"})
      ]
      obs_ft2 = deepcopy(observation_features)
      obs_ft2 = self.t.transform_observation_features(obs_ft2)
      self.assertEqual(
          obs_ft2,
          [ObservationFeatures(parameters={"a": 2.2, "b": "b"})],
      )
      obs_ft2 = self.t.untransform_observation_features(obs_ft2)
      self.assertEqual(obs_ft2, observation_features)
  
      observation_features = [
          ObservationFeatures(parameters={"a": 2.2, "b": "b", "c": "a"})
      ]
      observation_features_invalid = [
          ObservationFeatures(parameters={"a": 2.2, "b": "b", "c": "b"})
      ]
      # Fixed parameter out of design!
      with self.assertRaises(ValueError):
          self.t.transform_observation_features(
              observation_features_invalid
          )
  
file_path: Ax/ax/modelbridge/transforms/tests/test_remove_fixed_transform.py
imports: from copy import deepcopy
  from ax.core.observation import ObservationFeatures
  from ax.core.parameter import ChoiceParameter, FixedParameter, ParameterType, RangeParameter
  from ax.core.search_space import RobustSearchSpace, SearchSpace
  from ax.modelbridge.transforms.remove_fixed import RemoveFixed
  from ax.utils.common.testutils import TestCase
  from ax.utils.testing.core_stubs import get_robust_search_space
label_desc: Use image node_id 3 for calling the RemoveFixedTransformTest obj's underlying member method code with example usage: obj.test_TransformObservationFeatures() without return types