How to use extra_arguments that is included on composableNode()

edit

I have tried to use extra_arguments in order to pass arguments to composableNode. But it is not supposed to work I expect. Does anybody knows how to use this argument correctly? (I am using Dashing latest release version)

[robot.cpp]
robot::Robot::Robot(const rclcpp::NodeOptions & options)
: Node("robot", options)
{
  const std::vector<std::string> & args = options.arguments();
}

[launch.py]
        ComposableNodeContainer(
            node_name='robot',
            node_namespace='',
            package='rclcpp_components',
            node_executable='component_container',
            composable_node_descriptions=[
                ComposableNode(
                    package='robot',
                    node_plugin='robot::Robot',
                    node_name='robot',
                    parameters=[parameter_direction]),
                    # extra_arguments=[{'arguments': string_arg}]),
            ],
            output='screen'),

:)