code: def test_unset_config_env_vars(
      environment_variable: str,
      config_setting: str,
      value: Any,
      expected: str,
  ) -> None:
      assert environment_variable in _POLARS_CFG_ENV_VARS
  
      with pl.Config(**{config_setting: value}):
          assert os.environ[environment_variable] == expected
  
      with pl.Config(**{config_setting: None}):  # type: ignore[arg-type]
          assert environment_variable not in os.environ
  
imports: from __future__ import annotations
  import os
  from pathlib import Path
  from typing import Any, Iterator
  import pytest
  import polars
  import polars.polars
  from polars.config import _POLARS_CFG_ENV_VARS
label_desc: Use image node_id 19 for calling a global function with example usage: test_unset_config_env_vars(environment_variable, config_setting, value, expected) without return types