code: public T events_getMembers(Number eventId)
      throws FacebookException, IOException {
      assert (null != eventId);
      return this.callMethod(FacebookMethod.EVENTS_GET_MEMBERS,
                             new Pair<String, CharSequence>("eid", eventId.toString()));
    }
docs: Retrieves the membership list of an event
  @param eventId event id
  @return T consisting of four membership lists corresponding to RSVP status, with keys
  'attending', 'unsure', 'declined', and 'not_replied'