def _handle_response(self, transaction):
        """
        handles responses based on their type

        :param transaction:
        :return:
        """
        code = transaction.response.code
        utils.check_code(code)
        """
        VALID response:
        change the current cache value by switching the option set with the one provided
        also resets the timestamp
        if the request etag is different from the response, send the cached response
        """
        if code == Codes.VALID.number:
            logger.debug("received VALID")
            self.cache.validate(transaction.request, transaction.response)
            if transaction.request.etag != transaction.response.etag:
                element = self.cache.search_response(transaction.request)
                transaction.response = element.cached_response
            return transaction

        """
        CHANGED, CREATED or DELETED response:
        mark the requested resource as not fresh
        """
        if code == Codes.CHANGED.number or code == Codes.CREATED.number or code == Codes.DELETED.number:
            target = self.cache.search_related(transaction.request)
            if target is not None:
                for element in target:
                    self.cache.mark(element)
            return transaction

        """
        any other response code can be cached normally
        """
        self.cache.cache_add(transaction.request, transaction.response)
        return transaction
handles responses based on their type

        :param transaction:
        :return: