code: protected  String unset_string(nitro_service service, String id, options option, String args[]) throws Exception
  	{
  		Boolean warning = service.get_warning();
  		String result = service.get_payload_formatter().unset_string(this, id, option, args, warning);
  		return result;
  	}
docs: forms a String for unset operation on a resource.
  @param service nitro_service object.
  @param id session id.
  @param option Options object.
  @param args Array of args that are to be unset.
  @return  string in Json format.
  @throws Exception if invalid input is given.