code: def test_backend_variable_order(self, mock_secret_get, mock_meta_get):
      backends = ensure_secrets_loaded()
      backend_classes = [
          backend.__class__.__name__ for backend in backends
      ]
      assert "SystemsManagerParameterStoreBackend" in backend_classes
  
      mock_secret_get.return_value = None
      mock_meta_get.return_value = None
  
      assert "a_venv_value" == Variable.get(key="MYVAR")
      mock_secret_get.assert_called_with(key="MYVAR")
      mock_meta_get.assert_not_called()
  
      mock_secret_get.return_value = None
      mock_meta_get.return_value = "a_metastore_value"
      assert "a_metastore_value" == Variable.get(key="not_myvar")
      mock_meta_get.assert_called_once_with(key="not_myvar")
  
      mock_secret_get.return_value = "a_secret_value"
      assert "a_secret_value" == Variable.get(key="not_myvar")
  
imports: from __future__ import annotations
  from unittest import mock
  import pytest
  from airflow.configuration import ensure_secrets_loaded, initialize_secrets_backends
  from airflow.models import Connection, Variable
  from airflow.secrets.cache import SecretCache
  from tests.test_utils.config import conf_vars
  from tests.test_utils.db import clear_db_variables
label_desc: Use image node_id 6 for calling the TestVariableFromSecrets obj's underlying member method code with example usage: obj.test_backend_variable_order(mock_secret_get, mock_meta_get) without return types