code: def test_TransformObservationFeatures(self) -> None:
      observation_features = [self.observation_features]
      obs_ft2 = deepcopy(observation_features)
      obs_ft2 = self.t.transform_observation_features(obs_ft2)
      self.assertEqual(obs_ft2, [self.transformed_features])
      obs_ft2 = self.t.untransform_observation_features(obs_ft2)
      self.assertEqual(obs_ft2, observation_features)
      # Test partial transform
      obs_ft3 = [ObservationFeatures(parameters={"x": 2.2, "b": "b"})]
      obs_ft3 = self.t.transform_observation_features(obs_ft3)
      self.assertEqual(
          obs_ft3[0],
          ObservationFeatures(
              parameters={
                  "x": 2.2,
                  "b" + OH_PARAM_INFIX + "_0": 0,
                  "b" + OH_PARAM_INFIX + "_1": 1,
                  "b" + OH_PARAM_INFIX + "_2": 0,
              }
          ),
      )
      obs_ft5 = self.t.transform_observation_features(
          [ObservationFeatures({})]
      )
      self.assertEqual(obs_ft5[0], ObservationFeatures({}))
  
file_path: Ax/ax/modelbridge/transforms/tests/test_one_hot_transform.py
imports: from copy import deepcopy
  from ax.core.observation import ObservationFeatures
  from ax.core.parameter import ChoiceParameter, ParameterType, RangeParameter
  from ax.core.parameter_constraint import ParameterConstraint
  from ax.core.search_space import RobustSearchSpace, SearchSpace
  from ax.modelbridge.transforms.one_hot import OH_PARAM_INFIX, OneHot
  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 OneHotTransformTest obj's underlying member method code with example usage: obj.test_TransformObservationFeatures() without return types