extra.put("reloadable_stop", ReloadableStopFilterFactory::new);
        extra.put("flexible_porter_stem", FlexiblePorterStemFilterFactory::new);
        extra.put("alphanum_word", AlphaNumWordFilterFactory::new);
        extra.put("disable_graph", DisableGraphFilterFactory::new);
        return extra;
    }

    @Override

          "length" : 10
        },
        "truncate20_filter" : {
          "type" : "truncate",
          "length" : 20
        },
        "alphanum_word_filter" : {
          "type" : "alphanum_word",
          "max_token_length" : 20
        },
        "minhash_filter" : {
          "type" : "minhash",
          "seed" : 1,
          "bit" : 2,
          "size" : 64
        },