iOS RxSwift-如何使用Amb运算符?

我正在寻找RxSwift的Amb()操作符的示例。

let started = viewModel.networkAPI.filter { result in
            switch result {
            case .success:
                return true
            case .failure:
                return false
            }
        }

    let stopped = viewModel.networkAPI.filter { result in
        switch result {
        case .success:
            return true
        case .failure:
            return false
        }
    }

我试过:

    Observable<Bool>.amb([started, stopped])
//error - Ambiguous reference to member 'amb'
//Found this candidate (RxSwift.ObservableType)
//Found this candidate (RxSwift.ObservableType)

 started.amb(stopped)
//error - Generic parameter 'O2' could not be inferred

如何正确地使用RxSwift AMB操作符从两个观察值中选择一个首先发出一个值?