def handle_user(self, user_alias):
        self.join_user_groups(user_alias)
        users = self.api.people.list_contacts()['results']
        for user in users:
            if self._users.get(user['alias'], None) is None:
                self.handle_user(user['alias'])
                self._users[user['alias']] = True
                time.sleep(30)
            else:
                print('skip user: %s' % (user['alias']))