code: @Override
    public Firewall createFirewall(Firewall firewall)
        throws DigitalOceanException, RequestUnsuccessfulException {
      if (null == firewall || StringUtils.isBlank(firewall.getName())
          || firewall.getInboundRules().isEmpty() || firewall.getOutboundRules().isEmpty()) {
        throw new IllegalArgumentException(
            "Missing required parameters [Name, Inbound rules, Outbound rules] for create firewall.");
      }
      return (Firewall) perform(new ApiRequest(ApiAction.CREATE_FIREWALL, firewall)).getData();
    }
docs: ===========================================