code: public String toJSONString() {
          return TIME_PULLER.entrySet().stream()
                  .map(me -> String.format("%s: %d", me.getKey(), me.getValue().applyAsLong(this)))
                  .collect(Collectors.joining(", ", "{", "}"));
      }
docs: Represent this UStats as a name/value JSON structure.
  
  @return this data as a JSON-formatted string.