public static boolean isProto(SerializationFormat format) {
        requireNonNull(format, "format");
        return format == PROTO || format == PROTO_WEB || format == PROTO_WEB_TEXT;
    }
Is a proto-based gRPC serialization format.
grpc/src/main/java/com/linecorp/armeria/common/grpc/GrpcSerializationFormats.java