code: public String toJsonString() {
      	JSONArray jsonArray = new JSONArray();        
          for (LabeledItem<T> labeledItem : data) {
              JSONArray itemArray = new JSONArray();
              itemArray.put(labeledItem.getLabel());
              itemArray.put(labeledItem.getValue());
              jsonArray.put(itemArray);
          }
          JSONArray outerArray = new JSONArray();
          outerArray.put(jsonArray);
          return outerArray.toString();
      }
docs: /* (non-Javadoc)
  @see br.com.digilabs.jqplot.data.ChartData#toJsonString()