How to use the stevedore.DriverManager function in stevedore

def _load_driver(namespace, name):
    extension_manager = stevedore.DriverManager(
        namespace=namespace,
        name=name,
        invoke_on_load=True
    )
    LOG.info("Driver {name} successfully loaded".format(name=name))

    return extension_manager.driver

app.script_manager.add_command('createadminuser',
                                   auth_forms.CreateAdminUser)

    # Flask-Login, for Admin users.
    app.admin_login_manager = flask_login.LoginManager(app)
    # Set up callback to load user objects`
    app.admin_login_manager.user_loader(
        lambda user_id: db.session.query(models.AdminUser).get(user_id))

    # Use stevedore to load drivers/extensions.
    # Discover all drivers/extensions, but do not load any.
    # Used for logging found extensions.
    app.ext_mgr_all = stevedore.ExtensionManager(namespace='pg_discuss.ext')

    # Load configured IdentityPolicy driver
    app.identity_policy_loader = stevedore.DriverManager(
        namespace='pg_discuss.ext',
        name=app.config['DRIVER_IDENTITY_POLICY'],
    )
    # Initialize IdentityPolicyManager with configured IdentityManager
    app.identity_policy_mgr = identity.IdentityPolicyManager(
        app,
        app.identity_policy_loader.driver,
    )

    # Load configured CommentRenderer driver
    app.comment_renderer_loader = stevedore.DriverManager(
        namespace='pg_discuss.ext',
        name=app.config['DRIVER_COMMENT_RENDERER'],
    )
    app.comment_renderer = app.comment_renderer_loader.driver(app)

def get_handler(self, name: str) -> Callable[..., EventHandler]:
        """Get an handler class by name.

        Available handler classes are registered using the e3.event.handler
        entry_points in your setup.py

        :param name: handler name
        :return: an handler class
        """
        return stevedore.DriverManager("e3.event.handler", name).driver

def load_store(name: str, configuration: Any, cache: Cache) -> Store:
    plugin = stevedore.DriverManager("e3.store", name)

    return plugin.driver(configuration, cache)

def load_driver(driver_name, *args):
    namespace = 'keystone.unified_limit.model'
    try:
        driver_manager = stevedore.DriverManager(namespace,
                                                 driver_name,
                                                 invoke_on_load=True,
                                                 invoke_args=args)
        return driver_manager.driver
    except stevedore.exception.NoMatches:
        msg = (_('Unable to find %(name)r driver in %(namespace)r.'))
        raise ImportError(msg % {'name': driver_name, 'namespace': namespace})

def load_cache(name: str = "file-cache", configuration: Any = None) -> Cache:
    plugin = stevedore.DriverManager(namespace="e3.store.cache.backend", name=name)
    return plugin.driver(configuration)

def node_not_found_hook_manager(*args):
    global _NOT_FOUND_HOOK_MGR
    if _NOT_FOUND_HOOK_MGR is None:
        name = CONF.processing.node_not_found_hook
        if name:
            _NOT_FOUND_HOOK_MGR = stevedore.DriverManager(
                'ironic_inspector.hooks.node_not_found',
                name=name)

    return _NOT_FOUND_HOOK_MGR