How to use the observable-fns.multicast function in observable-fns

observe(selector: SelectorT, observe: () => ObservableLike) {
      const cacheKey = createCacheKey(selector)
      const cached = observables.get(cacheKey)

      if (cached) {
        return cached
      } else {
        // Multicast it, so we re-use the existing subscription
        // instead of setting up listeners over and over again
        const multicasted = multicast(observe())
        // TODO: Check if this value is actually newer than the old one
        observables.set(cacheKey, multicasted)
        return multicasted
      }
    }
  }

return ((...rawArgs: Args) => {
    const uid = nextJobUID++
    const { args, transferables } = prepareArguments(rawArgs)
    const runMessage: MasterJobRunMessage = {
      type: MasterMessageType.run,
      uid,
      method,
      args
    }
    debugMessages("Sending command to run function to worker:", runMessage)
    worker.postMessage(runMessage, transferables)
    return ObservablePromise.from(multicast(createObservableForJob(worker, uid)))
  }) as any as ProxyableFunction
}

export function subscribeToUpdatesAndPoll(
  implementation: SubscriberImplementation,
  options?: { retryFetchOnNoUpdate: boolean }
): Observable {
  const { retryFetchOnNoUpdate = true } = options || {}

  return multicast(
    new Observable(observer => {
      let cancelled = false

      let unsubscribe = () => {
        cancelled = true
      }

      const handleUnexpectedError = (error: Error) => {
        try {
          if (implementation.handleError) {
            implementation.handleError(error)
          } else {
            throw error
          }
        } catch (error) {
          observer.error(error)