code: func NewHelper(r *regexp.Regexp) (sm Helper) {
  	sm.IndexMap = make(map[string]int)
  	for i, name := range r.SubexpNames() {
  		sm.IndexMap[name] = i
  	}
  	sm.timeLayout = time.RFC3339
  	sm.regex = r
  	return
  }
docs: // NewHelper : creates a new submatch helper from a regexp struct