Makes sure that the given observable is being observed until the returned disposable is disposed,
after which there is no longer a guarantee that the observable is being observed by at least one observer.
This function can help keep the cache of a derived observable alive even when there might be no other observers.
Makes sure that the given observable is being observed until the returned disposable is disposed, after which there is no longer a guarantee that the observable is being observed by at least one observer.
This function can help keep the cache of a derived observable alive even when there might be no other observers.