code: protected void afterFork(List<Boolean> forks, long startTimeNanos) {
      int forksGenerated = 0;
      for (Boolean fork : forks) {
        forksGenerated += fork ? 1 : 0;
      }
      Instrumented.markMeter(this.outputForks, forksGenerated);
      Instrumented.updateTimer(this.forkOperatorTimer, System.nanoTime() - startTimeNanos, TimeUnit.NANOSECONDS);
    }
docs: Called after forkDataRecord.
  
  @param forks result from forkDataRecord.
  @param startTimeNanos start time of forkDataRecord.