def METHOD_NAME(self, save_dir=None):
    """Save a recommender model to the filesystem.
    Parameters
    ----------
    save_dir: str, default: None
        Path to a directory for the model to be stored.
    """
    if save_dir is None:
        return
    model_file = Recommender.METHOD_NAME(self, save_dir)
    # save TF weights
    self.saver.METHOD_NAME(self.sess, model_file.replace(".pkl", ".cpt"))
    return model_file