promql/value.go
func (vec Vector) ContainsSameLabelset() bool {
	l := make(map[uint64]struct{}, len(vec))
	for _, s := range vec {
		hash := s.Metric.Hash()
		if _, ok := l[hash]; ok {
			return true
		}
		l[hash] = struct{}{}
	}
	return false
}
func (vec Vector) ContainsSameLabelset() bool {
	l := make(map[uint64]struct{}, len(vec))
	for _, s := range vec {
		hash := s.Metric.Hash()
		if _, ok := l[hash]; ok {
			return true
		}
		l[hash] = struct{}{}
	}
	return false
}
// ContainsSameLabelset checks if a vector has samples with the same labelset
// Such a behavior is semantically undefined
// https://github.com/prometheus/prometheus/issues/4562