docs: def _validate_datetime_from_to(cls, start, end):
          """
          validate from-to
          :param start: Start Day(YYYYMMDD)
          :param end: End Day(YYYYMMDD)
          :return: None or MlbAmException
          """
          if not start <= end:
              raise MlbAmBadParameter("not Start Day({start}) <= End Day({end})".format(start=start, end=end))