Where is SaveToStorageStoreNotify?

I am working on learning Third Party Storage to save metadata on sketches, blocks in sketches, etc. The page:

https://help.solidworks.com/2021/english/api/sldworksapi/solidworks.interop.sldworks~solidworks.interop.sldworks.imodeldocextension~iget3rdpartystoragestore.html 

references an event 'SaveToStorageStoreNotify'. What object is this event defined in? I can find the description in the Solidworks help file but I don't see what class the event is defined in??? How Do I subscribe to this event?