ts.mutex.Lock()
	defer ts.mutex.Unlock()
	return ts.data.Copy(), ts.times.asDurationSinceEpoch(epoch)
}

type times []time.Time

func (t times) copy() times {
	out := make(times, 0, len(t))
	out = append(out, t...)
	return out
}

func (t times) asDurationSinceEpoch(epoch time.Time) []time.Duration {
	out := make([]time.Duration, 0, len(t))
	for _, tm := range t {