anchor.diff:      map["orderby"][fieldName] = order;
       return this;
     }
  +  SelectorBuilder sortByMetaTextScore(String fieldName){
  +    _ensureOrderBy();
  +    map["orderby"][fieldName] = {'\$meta' : "textScore"};
  +    return this;
  +  }
     SelectorBuilder hint(String fieldName, {bool descending: false}){
       _query;
       if (!map.containsKey("\$hint")){
  
positive.code:     return this;
    }
    SelectorBuilder sortBy(String fieldName, {bool descending: false}){
      _query;
      if (!map.containsKey("orderby")){
        map["orderby"] = new LinkedHashMap();
      }
      int order = 1;
      if (descending){
        order = -1;
  
negative.code:     return this;
    }
  
    SelectorBuilder metaTextScore(String fieldName) {
      _ensureParamFields();
      paramFields[fieldName] = {'\$meta' : "textScore"};
    }
  
    SelectorBuilder fields(List<String> fields) {
      _ensureParamFields();
      for (var field in fields) {
        paramFields[field] = 1;
      }
      return this;
    }
  
    SelectorBuilder excludeFields(List<String> fields) {
      _ensureParamFields();
      for (var field in fields) {
        paramFields[field] = 0;
      }
  