class LastOperation : AsyncOperation
{
    .....

    init() {
        super.init()
        ...
    }

    override func cancel() {
        task.cancel()
        super.cancel()
    }

    override func main() {
        guard  !isCancelled else { return  }

        guard let dependencyID = dependencies .compactMap({ ($0 as? FirstOperation)?.xxxx }).first else { return  }

        task = session.dataTask(...)
        task.resume()
    }
}