docs: 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