func mergeSamples(a, b []prompb.Sample) []prompb.Sample {
	result := make([]prompb.Sample, 0, len(a)+len(b))
	i, j := 0, 0
	for i < len(a) && j < len(b) {
		if a[i].Timestamp < b[j].Timestamp {
			result = append(result, a[i])
			i++
		} else if a[i].Timestamp > b[j].Timestamp {
			result = append(result, b[j])
			j++
		} else {
			result = append(result, a[i])
			i++
			j++
		}
	}
	result = append(result, a[i:]...)
	result = append(result, b[j:]...)
	return result
}
func mergeSamples(a, b []prompb.Sample) []prompb.Sample {
	result := make([]prompb.Sample, 0, len(a)+len(b))
	i, j := 0, 0
	for i < len(a) && j < len(b) {
		if a[i].Timestamp < b[j].Timestamp {
			result = append(result, a[i])
			i++
		} else if a[i].Timestamp > b[j].Timestamp {
			result = append(result, b[j])
			j++
		} else {
			result = append(result, a[i])
			i++
			j++
		}
	}
	result = append(result, a[i:]...)
	result = append(result, b[j:]...)
	return result
}
// mergeSamples merges two lists of sample pairs and removes duplicate
// timestamps. It assumes that both lists are sorted by timestamp.