code: def from_dict(d):
          
          start = d.get('start')
          end = d.get('end')
          if not (start and end):
              raise ValueError('DateRange must have both start and end')
          start = str_to_date(start)
          end = str_to_date(end)
          return DateRange(start, end)
docs: Transform the dict to a DateRange object.