code: def test_add_remove_modules(self):
      # TODO (Avnish): Modify this test to make sure that the distributed
      # functionality won't break the add / remove.
  
      env_class = make_multi_agent("CartPole-v0")
      env = env_class({"num_agents": 2})
      module = DiscreteBCTorchModule(
          config=RLModuleConfig(
              env.observation_space,
              env.action_space,
              model_config_dict={"fcnet_hiddens": [32]},
          )
      ).as_multi_agent()
  
      module.add_module(
          "test",
          DiscreteBCTorchModule(
              config=RLModuleConfig(
                  env.observation_space,
                  env.action_space,
                  model_config_dict={"fcnet_hiddens": [32]},
              )
          ),
      )
      self.assertEqual(set(module.keys()), {DEFAULT_POLICY_ID, "test"})
      module.remove_module("test")
      self.assertEqual(set(module.keys()), {DEFAULT_POLICY_ID})
  
      # test if add works with a conflicting name
      self.assertRaises(
          ValueError,
          lambda: module.add_module(
              DEFAULT_POLICY_ID,
              DiscreteBCTorchModule(
                  config=RLModuleConfig(
                      env.observation_space,
                      env.action_space,
                      model_config_dict={"fcnet_hiddens": [32]},
                  )
              ),
          ),
      )
  
      module.add_module(
          DEFAULT_POLICY_ID,
          DiscreteBCTorchModule(
              config=RLModuleConfig(
                  env.observation_space,
                  env.action_space,
                  model_config_dict={"fcnet_hiddens": [32]},
              )
          ),
          override=True,
      )
  
file_path: ray/python/ray/rllib/core/rl_module/tests/test_marl_module.py
imports: import tempfile
  import unittest
  from ray.rllib.core.rl_module.rl_module import SingleAgentRLModuleSpec, RLModuleConfig
  from ray.rllib.core.rl_module.marl_module import MultiAgentRLModule, MultiAgentRLModuleConfig
  from ray.rllib.core.testing.torch.bc_module import DiscreteBCTorchModule
  from ray.rllib.core.testing.utils import DEFAULT_POLICY_ID
  from ray.rllib.env.multi_agent_env import make_multi_agent
  from ray.rllib.utils.test_utils import check
label_desc: Use image node_id 4 for calling the TestMARLModule obj's underlying member method code with example usage: obj.test_add_remove_modules() without return types