docs: public R setFields(String... fields) {
          if (fields.length == 1 && fields[0] == null){
              mQueryMap.remove(QUERY_FIELDS);
              return (R) this;
          }
          if (fields.length > 0) {
              StringBuilder sb = new StringBuilder();
              sb.append(fields[0]);
              for (int i = 1; i < fields.length; ++i) {
                  sb.append(String.format(Locale.ENGLISH, ",%s", fields[i]));
              }
              mQueryMap.put(QUERY_FIELDS, sb.toString());
          }
  
          return (R) this;
      }