code: public static FeatureSet valueOf(String name) {
      switch (name) {
        case "es3":
          return ES3;
        case "es5":
          return ES5;
        case "es6-impl":
        case "es6":
          return ES6;
        case "typeCheckSupported":
          return TYPE_CHECK_SUPPORTED;
        case "es7":
          return ES7;
        case "es8":
          return ES8;
        case "es2018":
        case "es9":
          return ES2018;
        case "es_2019":
          return ES2019;
        case "es_next":
          return ES_NEXT;
        case "ts":
          return TYPESCRIPT;
        default:
          throw new IllegalArgumentException("No such FeatureSet: " + name);
      }
    }
docs: Parses known strings into feature sets.