code: def test_obs_preprocessor_connector(self):
      obs_space = gym.spaces.Dict(
          {
              "a": gym.spaces.Box(low=0, high=1, shape=(1,)),
              "b": gym.spaces.Tuple(
                  [
                      gym.spaces.Discrete(2),
                      gym.spaces.MultiDiscrete(nvec=[2, 3]),
                  ]
              ),
          }
      )
      ctx = ConnectorContext(config={}, observation_space=obs_space)
  
      c = ObsPreprocessorConnector(ctx)
      name, params = c.to_state()
  
      restored = get_connector(name, ctx, params)
      self.assertTrue(isinstance(restored, ObsPreprocessorConnector))
  
      obs = obs_space.sample()
      # Fake deterministic data.
      obs["a"][0] = 0.5
      obs["b"] = (1, np.array([0, 2]))
  
      d = AgentConnectorDataType(
          0,
          1,
          {
              SampleBatch.OBS: obs,
          },
      )
      preprocessed = c([d])
  
      # obs is completely flattened.
      self.assertTrue(
          (
              preprocessed[0].data[SampleBatch.OBS]
              == [0.5, 0, 1, 1, 0, 0, 0, 1]
          ).all()
      )
  
imports: import gymnasium
  from gymnasium.spaces import Box
  import numpy
  import tree
  import unittest
  from ray.rllib.algorithms.ppo.ppo import PPOConfig
  from ray.rllib.connectors.agent.clip_reward import ClipRewardAgentConnector
  from ray.rllib.connectors.agent.lambdas import FlattenDataAgentConnector
  from ray.rllib.connectors.agent.obs_preproc import ObsPreprocessorConnector
  from ray.rllib.connectors.agent.pipeline import AgentConnectorPipeline
  from ray.rllib.connectors.agent.state_buffer import StateBufferConnector
  from ray.rllib.connectors.agent.view_requirement import ViewRequirementAgentConnector
  from ray.rllib.connectors.connector import ConnectorContext
  from ray.rllib.connectors.registry import get_connector
  from ray.rllib.policy.view_requirement import ViewRequirement
  from ray.rllib.policy.sample_batch import SampleBatch
  from ray.rllib.utils.test_utils import check
  from ray.rllib.utils.typing import ActionConnectorDataType, AgentConnectorDataType, AgentConnectorsOutput
  from ray.rllib.connectors.agent.mean_std_filter import MeanStdObservationFilterAgentConnector
label_desc: Use image node_id 2 for calling the TestAgentConnector obj's underlying member method code with example usage: obj.test_obs_preprocessor_connector() without return types