code: def test_ray_labels_environment_variables(shutdown_only):
      os.environ[
          ray_constants.LABELS_ENVIRONMENT_VARIABLE
      ] = '{"custom1":"1", "custom2":"2"}'
      ray.init(labels={"custom1": "3", "custom3": "3"})
  
      node_info = ray.nodes()[0]
      assert node_info["Labels"]["custom1"] == "1"
      assert node_info["Labels"]["custom2"] == "2"
      assert node_info["Labels"]["custom3"] == "3"
  
imports: import glob
  import logging
  import multiprocessing
  import os
  import sys
  import tempfile
  import time
  from unittest import mock
  import numpy
  import psutil
  import pytest
  import ray
  import ray._private.gcs_utils
  import ray._private.ray_constants
  import ray._private.utils
  import ray.cluster_utils
  import ray.util.accelerators
  from ray._private.test_utils import wait_for_condition
  from ray.dashboard import k8s_utils
  from ray.runtime_env import RuntimeEnv
label_desc: Use image node_id 6 for calling a global function with example usage: test_ray_labels_environment_variables(shutdown_only) without return types