def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def __init__(self, region, name, retention_in_days=7):
    super(LogGroup, self).__init__()
    self.region = region
    self.name = name
    self.retention_in_days = retention_in_days