code: def test_custom_config_subclass(ray_start_4_cpus):
      test = TestBasic(
          1,
          True,
          {"train": 10},
          dataset_config=CustomConfig(),
      )
      test.fit()
  
imports: from typing import Optional
  import random
  import pytest
  from unittest.mock import MagicMock
  import ray
  from ray import train
  from ray.train import DataConfig, ScalingConfig
  from ray.data import DataIterator
  from ray.train.data_parallel_trainer import DataParallelTrainer
  from ray.data._internal.execution.interfaces.execution_options import ExecutionOptions
  from ray.tests.conftest import *
label_desc: Use image node_id 7 for calling a global function with example usage: test_custom_config_subclass(ray_start_4_cpus) without return types