@Nullable
    @Override
    public Boolean isResponseStreaming(Type returnType, @Nullable MediaType produceType) {
        final Class<?> clazz = typeToClass(unwrapUnaryAsyncType(returnType));
        if (clazz == null) {
            return null;
        }

        // Non-streaming types.
        if (isJson(produceType)) {
            return false;
        }
        if (Message.class.isAssignableFrom(clazz) && isProtobuf(produceType)) {
            return false;
        }

        // Streaming types
        if (isJsonSeq(produceType) &&
            (Publisher.class.isAssignableFrom(clazz) || Stream.class.isAssignableFrom(clazz))) {
            return true;
        }

        return null;
    }
Creates an instance with the specified {@link Printer}.
protobuf/src/main/java/com/linecorp/armeria/server/protobuf/ProtobufResponseConverterFunction.java