What kind of siri registration error will return

Hi,


Currenlty our project are integrating the func for `Add to siri`, we need to handle the callback from the shortcut controller inside the delegate of


INUIEditVoiceShortcutViewControllerDelegate & INUIAddVoiceShortcutViewControllerDelegate, we can see in the method

func addVoiceShortcutViewController(_ controller: INUIAddVoiceShortcutViewController,
                                        didFinishWith voiceShortcut: INVoiceShortcut?,
                                        error: Error?)

and

func editVoiceShortcutViewController(_ controller: INUIEditVoiceShortcutViewController,
                                         didUpdate voiceShortcut: INVoiceShortcut?,
                                         error: Error?)

We can see there can be error return, however, we don't know what kind of error will be return after searching the documents.
Could anyone help on clarifying this? Thanks a lot.