code: func parseSecurityRuleProtocol(proto string) (network.SecurityRuleProtocol, error) {
  	switch strings.ToLower(proto) {
  	case "tcp":
  		return network.TCP, nil
  	case "udp":
  		return network.UDP, nil
  	case "*":
  		return network.Asterisk, nil
  	default:
  		return "", fmt.Errorf("invalid protocol %s", proto)
  	}
  }
docs: // parseSecurityRuleProtocol parses a protocol string into a network.SecurityRuleProtocol
  // and returns error if the protocol is not supported