code: func (pot *partitionOffsetTracker) markAsProcessed(offset int64) bool {
  	pot.l.Lock()
  	defer pot.l.Unlock()
  	if offset > pot.highestProcessedOffset {
  		pot.highestProcessedOffset = offset
  		if pot.waitingForOffset == pot.highestProcessedOffset {
  			close(pot.done)
  		}
  		return true
  	} else {
  		return false
  	}
  }
docs: // MarkAsProcessed marks the provided offset as highest processed offset if
  // it's higher than any previous offset it has received.