@UnstableApi
    public static GrpcClientBuilder builder(SerializationFormat serializationFormat,
                                            HttpPreprocessor httpPreprocessor) {
        requireNonNull(serializationFormat, "serializationFormat");
        requireNonNull(httpPreprocessor, "httpPreprocessor");
        return new GrpcClientBuilder(serializationFormat, httpPreprocessor);
    }
Returns a new {@link GrpcClientBuilder} that builds the client that is configured with
the specified {@link HttpPreprocessor} and {@link SerializationFormat}.

<p>Note that if {@link SerializationFormat#NONE} is specified,
{@link GrpcSerializationFormats#PROTO} will be used by default.
grpc/src/main/java/com/linecorp/armeria/client/grpc/GrpcClients.java