Checking for `SS_List` sounds like the best solution.

I thought that `HasManyRelation.HasOneRelation` would be captured by `instanceof RelationList` but it isn't - the data when I tested this appeared as an `UnsavedRelationList` - not a `RelationList`. I don't know why that is happening, perhaps it's something I overlooked when setting up relations to test with, but checking for `instanceof SS_List` will be a good catch-all anyway.