code: func parseSubscriptionName(rawArgs json.RawMessage) (string, error) {
  	dec := json.NewDecoder(bytes.NewReader(rawArgs))
  	if tok, _ := dec.Token(); tok != json.Delim('[') {
  		return "", errors.New("non-array args")
  	}
  	v, _ := dec.Token()
  	method, ok := v.(string)
  	if !ok {
  		return "", errors.New("expected subscription name as first argument")
  	}
  	return method, nil
  }
docs: // parseSubscriptionName extracts the subscription name from an encoded argument array.