Parse ISO date string (YYYY-MM-DDTHH:mm:ss)

def from_iso_long_date(self, date_str: str) -> datetime:
        """ Parse ISO date string (YYYY-MM-DDTHH:mm:ss) """
        assert isinstance(date_str, str)
        assert len(date_str) == 19

        self.value = datetime.strptime(date_str, ISO_LONG_FORMAT)
        return self.value