def isoformat(self, sep='T'):
        """
        Formats the date as "%Y-%m-%d %H:%M:%S" with the sep param between the
        date and time portions

        :param set:
            A single character of the separator to place between the date and
            time

        :return:
            The formatted datetime as a unicode string in Python 3 and a byte
            string in Python 2
        """

        if self.microsecond == 0:
            return self.strftime('0000-%%m-%%d%s%%H:%%M:%%S' % sep)
        return self.strftime('0000-%%m-%%d%s%%H:%%M:%%S.%%f' % sep)