esp-idf/tools/test_idf_py/extra_path/some_ext.py

def action_extensions(base_actions, project_path):
    def some_callback(ut_apply_config_name, ctx, args):
        print('!!! From some subcommand')

    def some_global_callback(ctx, global_args, tasks):
        print('!!! From some global callback: %s' % global_args.some_extension_option)

    return {
        'global_options': [{
            'names': ['--some-extension-option'],
            'help': 'Help for option --some-extension-option',
            'default': 'test',
        }],
        'global_action_callbacks': [some_global_callback],
        'actions': {
            'extra_subcommand': {
                'callback': some_callback,
                'help': 'Help for some subcommand.',
            },
        },
    }