Retrieves any updates from the Telegram API.
        Registered listeners and applicable message handlers will be notified when a new message arrives.
        :raises ApiException when a call has failed.

def __retrieve_updates(self, timeout=20):
        """
        Retrieves any updates from the Telegram API.
        Registered listeners and applicable message handlers will be notified when a new message arrives.
        :raises ApiException when a call has failed.
        """
        if self.skip_pending:
            logger.debug('Skipped {0} pending messages'.format(self.__skip_updates()))
            self.skip_pending = False
        updates = self.get_updates(offset=(self.last_update_id + 1), timeout=timeout)
        self.process_new_updates(updates)