code: protected boolean isElementLate(StreamRecord<IN> element){
  		return (windowAssigner.isEventTime()) &&
  			(element.getTimestamp() + allowedLateness <= internalTimerService.currentWatermark());
  	}
docs: Decide if a record is currently late, based on current watermark and allowed lateness.
  
  @param element The element to check
  @return The element for which should be considered when sideoutputs