code: func NewKVKeysQuery(s string) (*KVKeysQuery, error) {
  	if s != "" && !KVKeysQueryRe.MatchString(s) {
  		return nil, fmt.Errorf("kv.keys: invalid format: %q", s)
  	}
  
  	m := regexpMatch(KVKeysQueryRe, s)
  	return &KVKeysQuery{
  		stopCh: make(chan struct{}, 1),
  		dc:     m["dc"],
  		prefix: m["prefix"],
  	}, nil
  }
docs: // NewKVKeysQuery parses a string into a dependency.