code: def test_update_non_existing_var_should_raise_key_error(self):
      with pytest.raises(KeyError):
          Variable.update("thisIdDoesNotExist", "value")
  
imports: from __future__ import annotations
  import logging
  import os
  from unittest import mock
  import pytest
  from cryptography.fernet import Fernet
  from airflow import settings
  from airflow.models import Variable, crypto, variable
  from airflow.secrets.cache import SecretCache
  from airflow.secrets.metastore import MetastoreBackend
  from tests.test_utils import db
  from tests.test_utils.config import conf_vars
label_desc: Use image node_id 16 for calling the TestVariable obj's underlying member method code with example usage: obj.test_update_non_existing_var_should_raise_key_error() without return types