docs: def validate_maintenance_window(window):
      """Validate PreferredMaintenanceWindow for DBInstance"""
  
      days = ("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")
      day_re = r'[A-Z]{1}[a-z]{2}'
      hour = r'[01]?[0-9]|2[0-3]'
      minute = r'[0-5][0-9]'
      r = ("(?P<start_day>%s):(?P<start_hour>%s):(?P<start_minute>%s)-"
           "(?P<end_day>%s):(?P<end_hour>%s):(?P<end_minute>%s)") % (day_re,
                                                                     hour,
                                                                     minute,
                                                                     day_re,
                                                                     hour,
                                                                     minute)
      range_regex = re.compile(r)
      m = range_regex.match(window)
      if not m:
          raise ValueError("DBInstance PreferredMaintenanceWindow must be in "
                           "the format: ddd:hh24:mi-ddd:hh24:mi")
      if m.group('start_day') not in days or m.group('end_day') not in days:
          raise ValueError("DBInstance PreferredMaintenanceWindow day part of "
                           "ranges must be one of: %s" % ", ".join(days))
      start_ts = (days.index(m.group('start_day')) * 24 * 60) + \
          (int(m.group('start_hour')) * 60) + int(m.group('start_minute'))
      end_ts = (days.index(m.group('end_day')) * 24 * 60) + \
          (int(m.group('end_hour')) * 60) + int(m.group('end_minute'))
      if abs(end_ts - start_ts) < 30:
          raise ValueError("DBInstance PreferredMaintenanceWindow must be at "
                           "least 30 minutes long.")
      return window