code: def test_cli_show_config_should_display_key(self):
      with contextlib.redirect_stdout(StringIO()) as temp_stdout:
          config_command.show_config(
              self.parser.parse_args(
                  ["config", "list", "--color", "off"]
              )
          )
      output = temp_stdout.getvalue()
      assert "[core]" in output
      assert "testkey = test_value" in temp_stdout.getvalue()
  
imports: from __future__ import annotations
  import contextlib
  from io import StringIO
  from unittest import mock
  import pytest
  from airflow.cli import cli_parser
  from airflow.cli.commands import config_command
  from tests.test_utils.config import conf_vars
label_desc: Use image node_id 4 for calling the TestCliConfigList obj's underlying member method code with example usage: obj.test_cli_show_config_should_display_key() without return types