:type record: aiologger.loggers.json.LogRecord

def format(self, record) -> str:
        """
        :type record: aiologger.loggers.json.LogRecord
        """
        msg = dict(self.formatter_fields_for_record(record))
        if record.flatten and isinstance(record.msg, dict):
            msg.update(record.msg)
        else:
            msg[MSG_FIELDNAME] = record.msg

        if record.extra:
            msg.update(record.extra)
        if record.exc_info:
            msg["exc_info"] = record.exc_info
        if record.exc_text:
            msg["exc_text"] = record.exc_text

        return self.serializer(
            msg, default=self._default_handler, **record.serializer_kwargs
        )