docs: def quarter_to_daterange(quarter):
      """Convert a quarter in arbitrary filename-ready format (e.g. 2015Q1)
      into start and end datetimes"""
      assert len(quarter) == 6
      year = int(quarter[0:4])
      quarter = quarter[5]
      MONTH_DAY = {
          '1': ((1, 1), (3, 31)),
          '2': ((4, 1), (6, 30)),
          '3': ((7, 1), (9, 30)),
          '4': ((10, 1), (12, 31))
      }
      md = MONTH_DAY[quarter]
      start_md, end_md = md
      return (
          date(year, *start_md),
          date(year, *end_md)
      )