code: def test_missing_default_secrets_backend_type(self):
      self.assertIsNone(
          metaflow.metaflow_config.DEFAULT_SECRETS_BACKEND_TYPE
      )
      # assumes DEFAULT_SECRETS_BACKEND_TYPE is None when we run this test
      with self.assertRaises(MetaflowException):
          SecretSpec.secret_spec_from_str("secret_id", None)
  
file_path: metaflow/test/unit/test_secrets_decorator.py
imports: import os
  import time
  import unittest
  from unittest.mock import patch
  from metaflow.exception import MetaflowException
  import metaflow.metaflow_config
  from metaflow.plugins.secrets.secrets_decorator import SecretSpec, validate_env_vars_across_secrets, validate_env_vars_vs_existing_env, validate_env_vars, get_secrets_backend_provider
label_desc: Use image node_id 1 for calling the TestSecretsDecorator obj's underlying member method code with example usage: obj.test_missing_default_secrets_backend_type() without return types