Note that we are using proto2 semantics, where all fields are explicitly required or optional.

Its a shame, would proto3 not be a better target?

@sandwwraith Can comment on that

AFAIK, you can serialize your classes in proto2 semantics, and it can be normally deserialized in proto3. In deserialization, proto3 provides very unhandy semantics - each field can be represented in stream one or zero times. It means that any field implicitly is optional, which in my opinion is not very idiomatic