docs: public JSONObject accumulate(String key, Object value) throws JSONException {
          testValidity(value);
          Object object = this.opt(key);
          if (object == null) {
              this.put(key,
                      value instanceof JSONArray ? new JSONArray().put(value)
                              : value);
          } else if (object instanceof JSONArray) {
              ((JSONArray) object).put(value);
          } else {
              this.put(key, new JSONArray().put(object).put(value));
          }
          return this;
      }