/** The key of the configuration. e.g. 200 */
    String RANK_FUSION_window_size = "rank.fusion.window_size";

    /** The key of the configuration. e.g. 20 */
    String RANK_FUSION_rank_constant = "rank.fusion.rank_constant";

    /** The key of the configuration. e.g. -1 */
    String RANK_FUSION_THREADS = "rank.fusion.threads";

    /** The key of the configuration. e.g. rf_score */