ACS query sel not working as expected

I couldn't find any proper example for what I found in the documentation:

"If you want to display a field from a nested object, then both the name of the nested object and field need to be specified."

So, it seems, if I'm querying for places and want to have the photo.urls.original url associated with the place, I need to write something like this:

ACS.Places.query({
        where: {
            //whatever the condition may be
            }
        }
        ,sel: JSON.stringify({"all": ["id", "name", "address", "city", "postal_code", "latitude", "longitude", "photo", "photo.urls", "photo.urls.original"]})
    } , function (e) {
//and so on
}

What's the error in my code?