Where does Photos store iCloud photos shared with me? What is the location where Apple Photos stores Shared photos? I'm looking for the photos that appear under the Shared tab, to view them in the Finder.

My particular reason is that I'd like to enable these photos to be backed up by Google Photos Desktop Uploader. All of my own photos are being synced to Google, but not the ones that are shared with me. If I can find the local copy, I can turn it on in the uploader preferences.
I found the local storage location for iCloud shared images.

cd "/Users/simon/Library/Containers/com.apple.cloudphotosd/Data/Library/Application Support/com.apple.cloudphotosd/services/com.apple.photo.icloud.sharedstreams/assets"


Replace simon with your username.

Of course, the ridiculous obscurity of this path means they'll probably change it again, but this is what it is as of OS X 10.12.5 and Photos Version 2.0 (3150.4.120).