code: def test_custom_train_fn(self):
      with ray_start_client_server():
          assert ray.util.client.ray.is_connected()
  
          config = {
              # Special flag signalling `my_train_fn` how many iters to do.
              "train-iterations": 2,
              "lr": 0.01,
              # Use GPUs iff `RLLIB_NUM_GPUS` env var set to > 0.
              "num_gpus": int(os.environ.get("RLLIB_NUM_GPUS", "0")),
              "num_workers": 0,
              "framework": "tf",
          }
          resources = ppo.PPO.default_resource_request(config)
          from ray.rllib.examples.custom_train_fn import my_train_fn
  
          tune.Tuner(
              tune.with_resources(my_train_fn, resources),
              param_space=config,
          ).fit()
  
file_path: ray/python/ray/rllib/tests/test_ray_client.py
imports: import os
  import sys
  import unittest
  import pytest
  import ray
  from ray import air
  from ray import tune
  import ray.rllib.algorithms.ppo
  from ray.rllib.examples.env.stateless_cartpole import StatelessCartPole
  from ray.util.client.ray_client_helpers import ray_start_client_server
label_desc: Use image node_id 2 for calling the TestRayClient obj's underlying member method code with example usage: obj.test_custom_train_fn() without return types