code: public static PollResult createIncremental(Map<String, Object> added, 
              Map<String, Object> changed, Map<String, Object> deleted, Object checkPoint) {
          return new PollResult(added, changed, deleted, checkPoint);
      }
docs: Create a result that represents incremental changes from the configuration
  source.
  
  @param added properties added
  @param changed properties changed
  @param deleted properties deleted, in which case the value in the map will be ignored
  @param checkPoint Object that served as a marker for this incremental change, for example, a time stamp
  of the last change.