The documentation has incorrect signature. There is no RTC.init method. The RTC.datetime method has a different signature: it has no tzinfo parameter, and the "day of week" parameter follows the day parameter (instead of the hour).

For details see: https://stackoverflow.com/questions/49757733/micropython-on-esp8266-rtc-does-not-have-an-init-method/49758737#49758737