code: def test_env_var_override():
      with unittest.mock.patch.dict(
          os.environ, {"RAY_NAMESPACE": "envName"}
      ), ray_start_client_server() as given_connection:
          given_connection.disconnect()
  
          with ray.init("ray://localhost:50051"):
              assert ray.get_runtime_context().namespace == "envName"
  
imports: import logging
  import os
  import sys
  import unittest.mock
  import tempfile
  import shutil
  from unittest.mock import patch
  import pytest
  import ray
  from ray._private.ray_constants import RAY_OVERRIDE_DASHBOARD_URL, DEFAULT_RESOURCES
  from ray.air.util.node import _get_node_id_from_node_ip
  import ray._private.services
  from ray._private.services import get_node_ip_address
  from ray.dashboard.utils import ray_address_to_api_server_url
  from ray._private.test_utils import get_current_unused_port, run_string_as_driver, wait_for_condition
  from ray.util.client.ray_client_helpers import ray_start_client_server
label_desc: Use image node_id 6 for calling a global function with example usage: test_env_var_override() without return types