group_by_products_ids not found

[balen]

Using Rails 4.0.4 with Spree stable 2.2. When I install spree product groups and try to create a group I get an exception stating that group_by_products_id is not a valid method.
I fixed this locally by changing line 125 of file /app/models/spree/product_group.rb to the following:

apply_on(Product.group :id, use_order)

I am not sure if this is what is intended as I am not sure what what product groups is used for. I was investigating various spree plugins to see if I could create dynamic relationships between products for bundles.