start
abstract suspend fun <T> startOnce(filter: String? = null, setPresence: Presence? = null, currentBatchToken: MutableStateFlow<String?> = MutableStateFlow(null), timeout: Long = 0, withTransaction: suspend (block: suspend () -> Unit) -> Unit = { it() }, asUserId: UserId? = null, runOnce: suspend (Sync.Response) -> T): Result<T>