code: static JSONObject addSource(JSONObject params) {
          if (params == null) {
              params = new JSONObject();
          }
          try {
              params.put("source", "android");
          } catch (JSONException e) {
              e.printStackTrace();
          }
          return params;
      }
docs: Convert the given JSONObject to string and adds source value as
  
  @param params JSONObject to convert to string
  @return A {@link String} value representing the JSONObject