code: func (p *Backoff) IsInBackOffSince(id string, eventTime time.Time) bool {
  	p.Lock()
  	defer p.Unlock()
  	entry, ok := p.perItemBackoff[id]
  	if !ok {
  		return false
  	}
  	if hasExpired(eventTime, entry.lastUpdate, p.maxDuration) {
  		return false
  	}
  	return p.Clock.Now().Sub(eventTime) < entry.backoff
  }
docs: // Returns True if the elapsed time since eventTime is smaller than the current backoff window