code: def test_teardown():
      """Test that the GROUP_RANK substitutes NODE_RANK."""
      env = LightningEnvironment()
      assert "WORLD_SIZE" in os.environ
      env.teardown()
      assert "WORLD_SIZE" not in os.environ
  
file_path: pytorch-lightning/tests/tests_fabric/plugins/environments/test_lightning.py
imports: import os
  from unittest import mock
  import pytest
  from lightning.fabric.plugins.environments import LightningEnvironment
label_desc: Use image node_id 6 for calling a global function with example usage: test_teardown() without return types