@Nullable
    static String serializationFormat(RequestLog requestLog) {
        final SerializationFormat serFmt = requestLog.scheme().serializationFormat();
        return serFmt == SerializationFormat.NONE ? null : serFmt.uriText();
    }
Returns the {@link SerializationFormat#uriText()} if it's not {@link SerializationFormat#NONE}.
brave/brave6/src/main/java/com/linecorp/armeria/server/brave/ServiceRequestContextAdapter.java