Hi! I am starting out with cl-protobufs. I would like to interact with a service that is doing the equivalent of the following line of Python, which allows polymorphic treatement of animals, creating a cat and serializing it for transmission to a recipient expecting an Animal (the base message). animal = Animal() animal.type = Animal.Cat cat = animal.Extensions[Cat.animal] # now work with cat... # now serialize animal ... That example is from the tutorial at http://www.indelible.org/ink/protobuf-polymorphism/ which shows the .proto file containing Animal, Cat and Dog messages. How would this code look in cl-protobufs? I'd be most grateful for any clues. I couldn't see anything like like this in the examples (but I admit I'm totally new to the protobufs concepts, and rusty at Lisp, so might have missed it...). Thanks! Thomas