public TxResult<Boolean> run() {
Key<Conference> conferenceKey = Key.create(websafeConferenceKey);
Conference conference = ofy().load().key(conferenceKey).now();
// 404 when there is no Conference with the given conferenceId.
if (conference == null) {
return new TxResult<>(new NotFoundException(
"No Conference found with key: " + websafeConferenceKey));
}
// Un-registering from the Conference.
Profile profile = getProfileFromUser(user, userId);
if (profile.getConferenceKeysToAttend().contains(websafeConferenceKey)) {