Delete items using Apple's new api NSFileProviderReplicatedExtension

Question

We are using Apple's new api NSFileProviderReplicatedExtension to implement a file provider extension. We can use this extension to synchronize files from a remote file server.When there are changes on the server，we can signal workingset to update the local copy. But when a directory with many files is deleted on the server, we can't delete this directory by calling observer.didDeleteItems.Can someone give me some advice? The Apple's documents is here:enter link description here