def SetDayOfWeekHasService(self, dow, has_service=True):
    """Set service as running (or not) on a day of the week. By default the
    service does not run on any days.

    Args:
      dow: 0 for Monday through 6 for Sunday
      has_service: True if this service operates on dow, False if it does not.

    Returns:
      None
    """
    assert(dow >= 0 and dow < 7)
    self.day_of_week[dow] = has_service