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;
    }