How to access map key/value pair contained in a ModelMap object from jsp Spring MVC

I have a ModelMap variable "model", the value object contained in the model map itself is a HashMap.

Controller code:

public @ResponseBody String func(ModelMap model) 
{
    HashMap<String, List<String> aMap = new HashMap<String, List<String>();
    ArrayList<String> aList = new ArrayList<String>();
    ....// give aList some data
    aMap.put("keystring", aList);
    model.addAttribute("aMap", aMap); 

    String view = "test";
    return view;
}

test.jsp code:

 var data = '${aMap}'; 
 // I know this gets the entire aMap including its key ("keystring") 
 // and the value (aList)

How do I access aMap's key ("keyString") and the value (aList) from test.jsp script part ? Any help will be appreciated.