docs: def get_start_date(module, x):
      """ 曜日による最初の授業の日を返す """
      weekdays = ['月', '火', '水', '木', '金', '土', '日']
      a, b = parse_module(module)
      module = a + b[0]
  
      d = datetime.datetime(*start_dates[module])
      days = weekdays.index(x) - d.weekday()
      if days < 0:
          days += 7
      delta = datetime.timedelta(days=days)
      return d + delta