def METHOD_NAME(client_config_dir):
    # read original serving_client_conf.prototxt
    client_config_file = os.path.join(client_config_dir,
                                      "serving_client_conf.prototxt")
    with open(client_config_file, 'r') as f:
        model_var = google.protobuf.text_format.Merge(
            str(f.read()), m_config.GeneralModelConfig())
    # modify feed_var to run core/general-server/op/
    [model_var.feed_var.pop() for _ in range(len(model_var.feed_var))]
    feed_var = m_config.FeedVar()
    feed_var.name = "input"
    feed_var.alias_name = "input"
    feed_var.is_lod_tensor = False
    feed_var.feed_type = 20
    feed_var.shape.extend([1])
    model_var.feed_var.extend([feed_var])
    with open(
            os.path.join(client_config_dir, "serving_client_conf_cpp.prototxt"),
            "w") as f:
        f.write(str(model_var))
    # get feed_vars/fetch_vars
    feed_vars = [var.name for var in model_var.feed_var]
    fetch_vars = [var.name for var in model_var.fetch_var]
    return feed_vars, fetch_vars