ok, right. i think it could be made clearer what providing multiple subjects in a call to

product_request()

is supposed to do. the current i think implies that you can provide multiple subjects and that's supposed to resolve to a single product (which is why e.g. i thought you could provide each of

[Select(A), Select(B), Select(C)]

as `RootRule`s):

Executes a request for a single product for some subjects, and returns the products.