def METHOD_NAME(exe, program, save_dir, model_name, postfix=None):
    """save_model"""
    model_path = os.path.join(save_dir, model_name + postfix)
    if os.path.isdir(model_path):
        shutil.rmtree(model_path)
    paddle.fluid.io.save_persistables(exe,
                               save_dir,
                               main_program=program,
                               filename=model_path)