def iso8601(
        self,
        tzinfo: Optional[TzInfo] = None,
        end_datetime: Optional[DateParseType] = None,
        sep: str = "T",
        timespec: str = "auto",
    ) -> str:
        """
        Get an ISO 8601 string for a datetime between the UNIX epoch and now.

        :param tzinfo: timezone, instance of datetime.tzinfo subclass
        :param end_datetime: A ``DateParseType``. Defaults to the current date and time
        :param sep: separator between date and time, defaults to 'T'
        :param timespec: format specifier for the time part, defaults to 'auto' - see datetime.isoformat() documentation

        :sample:
        """
        return self.date_time(tzinfo, end_datetime=end_datetime).isoformat(sep, timespec)

        Get an ISO 8601 string for a datetime between the UNIX epoch and now.

        :param tzinfo: timezone, instance of datetime.tzinfo subclass
        :param end_datetime: A ``DateParseType``. Defaults to the current date and time
        :param sep: separator between date and time, defaults to 'T'
        :param timespec: format specifier for the time part, defaults to 'auto' - see datetime.isoformat() documentation

        :sample:
        
faker/providers/date_time/__init__.py