code: def test_resources_different():
      resource_1 = _Resources(
          1, 0, 0, 1, custom_resources={"a": 1, "b": 2}
      )
      resource_2 = _Resources(
          1, 0, 0, 1, custom_resources={"a": 1, "c": 2}
      )
      new_res = _Resources.subtract(resource_1, resource_2)
      assert "c" in new_res.custom_resources
      assert "b" in new_res.custom_resources
  
      assert new_res.cpu == 0
      assert new_res.gpu == 0
      assert new_res.extra_cpu == 0
      assert new_res.extra_gpu == 0
      assert new_res.get("a") == 0
  
file_path: ray/python/ray/tune/tests/test_resource_updater.py
imports: import ray
  from ray.tests.conftest import *
  from ray.tune.utils.resource_updater import _ResourceUpdater, _Resources
  from unittest import mock
label_desc: Use image node_id 3 for calling a global function with example usage: test_resources_different() without return types