code: func GetNextEpoch(last Epoch, now uint64) Epoch {
  	if last == NoClue {
  		return GetFirstEpoch(now)
  	}
  	level := GetNextLevel(last, now)
  	return Epoch{
  		Level: level,
  		Time:  now,
  	}
  }
docs: // GetNextEpoch returns the epoch where the next update should be located
  // according to where the previous update was
  // and what time it is now.