https://codelabs.developers.google.com/codelabs/android-workmanager-kt/

BlurViewModel.kt

class BlurViewModel : ViewModel() {

    ...
    
    internal fun applyBlur(blurLevel: Int) {
        val chargingConstraints = Constraints.Builder()
            .setRequiresCharging(true)
            .build()

        val cleanupRequest = OneTimeWorkRequest
            .Builder(CleanupWorker::class.java)
            .build()

        val blurRequests = (0 until blurLevel).mapIndexed { index, _ ->
            OneTimeWorkRequestBuilder<BlurWorker>()
                .apply {
                    if (index == 0) {
                        setInputData(createInputDataForUri())
                    }
                }
                .build()
        }

        val saveRequest = OneTimeWorkRequest
            .Builder(SaveImageToFileWorker::class.java)
            .setConstraints(chargingConstraints)
            .addTag(TAG_OUTPUT)
            .build()

        workManager
            .beginUniqueWork(
                IMAGE_MANIPULATION_WORK_NAME,
                ExistingWorkPolicy.REPLACE,
                cleanupRequest
            )
            .thenSequentially(blurRequests)
            .then(saveRequest)
            .enqueue()
    }

    // WorkContinuation#then(List<OneTimeWorkRequest>)는 'in any order'라서 임의로 sequential then을 추가함
    private fun WorkContinuation.thenSequentially(
        works: List<OneTimeWorkRequest>
    ): WorkContinuation {
        var continuation = this
        works.forEach {
            continuation = continuation.then(it)
        }
        return continuation
    }