code: def parse(self, s):
          
          # TODO: can we use xml.utils.iso8601 or something similar?
  
          from luigi import date_interval as d
  
          for cls in [d.Year, d.Month, d.Week, d.Date, d.Custom]:
              i = cls.parse(s)
              if i:
                  return i
  
          raise ValueError('Invalid date interval - could not be parsed')
docs: Parses a :py:class:`~luigi.date_interval.DateInterval` from the input.
  
          see :py:mod:`luigi.date_interval`
            for details on the parsing of DateIntervals.