You can have conditional protobuf fields / messages.

Checkout:

- Any: https://developers.google.com/protocol-buffers/docs/proto3#a...

- OneOf: https://developers.google.com/protocol-buffers/docs/proto3#o...

I believe Any is the equivalent to having a proto in format of:

```

message MyMessage {

    string type = 1;

    bytes data = 2;

}

```