Implementing generic interface method outside of interface definition

Hi Racketeers,

I am learning Racket and busy working through Generic Interfaces. I was wondering if it is possible to provide an implementation for a generic interface outside of the (struct) form definition.

For example, lets say I use a 3rd-party library that provides a stringify generic interface. I would like to implement that interface for numbers, but I do not have access to the generic interface definition.

Is it still possible in this case to provide an implementation for the generic interface? Or is this just a limitation of the generic interface facility?