code: public static vm_device[] get_filtered(nitro_service service, String filter) throws Exception
  	{
  		vm_device obj = new vm_device();
  		options option = new options();
  		option.set_filter(filter);
  		vm_device[] response = (vm_device[]) obj.getfiltered(service, option);
  		return response;
  	}
docs: Use this API to fetch filtered set of vm_device resources.
  filter string should be in JSON format.eg: "vm_state:DOWN,name:[a-z]+"