code: public static base_response sign(nitro_service client, dnszone resource) throws Exception {
  		dnszone signresource = new dnszone();
  		signresource.zonename = resource.zonename;
  		signresource.keyname = resource.keyname;
  		return signresource.perform_operation(client,"sign");
  	}
docs: Use this API to sign dnszone.