class Device(object):
    def __del__(self):
        print("Device!")


class Vector(object):
    def __init__(self, device):
        self.device = device

    def __del__(self):
        print("Vector!")


class DeviceHolder(object):
    def __init__(self, device):
        self.device = device


class VectorHolder(object):
    def __init__(self, vector):
        self.vector = vector


def main():
    d = Device()
    v = Vector(d)
    a = DeviceHolder(d)
    b = VectorHolder(v)
    a.b = b
    b.a = a


if __name__ == "__main__":
    main()