clientv3/concurrency/stm.go
func (rs readSet) cmps() []v3.Cmp {
	cmps := make([]v3.Cmp, 0, len(rs))
	for k, rk := range rs {
		cmps = append(cmps, isKeyCurrent(k, rk))
	}
	return cmps
}
func (rs readSet) cmps() []v3.Cmp {
	cmps := make([]v3.Cmp, 0, len(rs))
	for k, rk := range rs {
		cmps = append(cmps, isKeyCurrent(k, rk))
	}
	return cmps
}
func ( rs readSet ) cmps ( ) [ ] v3 . Cmp { cmps := make ( [ ] v3 . Cmp , 0 , len ( rs ) ) for k , rk := range rs { cmps = append ( cmps , isKeyCurrent ( k , rk ) ) } return cmps }
// cmps guards the txn from updates to read set
cmps guards the txn from updates to read set