Iterate over fetched_records

def _message_generator(self):
        """Iterate over fetched_records"""
        while self._next_partition_records or self._completed_fetches:

            if not self._next_partition_records:
                completion = self._completed_fetches.popleft()
                self._next_partition_records = self._parse_fetched_data(completion)
                continue

            # Send additional FetchRequests when the internal queue is low
            # this should enable moderate pipelining
            if len(self._completed_fetches) <= self.config['iterator_refetch_records']:
                self.send_fetches()

            tp = self._next_partition_records.topic_partition

            # We can ignore any prior signal to drop pending message sets
            # because we are starting from a fresh one where fetch_offset == position
            # i.e., the user seek()'d to this position
            self._subscriptions.assignment[tp].drop_pending_message_set = False

            for msg in self._next_partition_records.take():

                # Because we are in a generator, it is possible for
                # subscription state to change between yield calls
                # so we need to re-check on each loop
                # this should catch assignment changes, pauses
                # and resets via seek_to_beginning / seek_to_end
                if not self._subscriptions.is_fetchable(tp):
                    log.debug("Not returning fetched records for partition %s"
                              " since it is no longer fetchable", tp)
                    self._next_partition_records = None
                    break

                # If there is a seek during message iteration,
                # we should stop unpacking this message set and
                # wait for a new fetch response that aligns with the
                # new seek position
                elif self._subscriptions.assignment[tp].drop_pending_message_set:
                    log.debug("Skipping remainder of message set for partition %s", tp)
                    self._subscriptions.assignment[tp].drop_pending_message_set = False
                    self._next_partition_records = None
                    break

                # Compressed messagesets may include earlier messages
                elif msg.offset < self._subscriptions.assignment[tp].position:
                    log.debug("Skipping message offset: %s (expecting %s)",
                              msg.offset,
                              self._subscriptions.assignment[tp].position)
                    continue

                self._subscriptions.assignment[tp].position = msg.offset + 1
                yield msg

            self._next_partition_records = None