Serialize values like date and time. Respect other values:
        :return:

def _serialize_value(self, value):
        """
        Serialize values like date and time. Respect other values:
        :return:
        """

        if isinstance(value, datetime.datetime):
            return value.strftime(self.datetime_format)
        elif isinstance(value, datetime.date):
            return value.strftime(self.date_format)
        elif isinstance(value, datetime.time):
            return value.strftime(self.time_format)
        return text_type(value)