@Override
    public String toString() {
        return "DocumentOperationParameters{" +
               "priority=" + priority +
               ", fieldSet='" + fieldSet + '\'' +
               ", route='" + route + '\'' +
               ", traceLevel=" + traceLevel +
               '}';
    }
Sets the {@link ResponseHandler} to handle the {@link Response} of an async operation, instead of the session default.
documentapi/src/main/java/com/yahoo/documentapi/DocumentOperationParameters.java