@Override
    public void write(DocWriter writer, String previousText, ShapeSubheadingSection section) {
        writer.writeBadge(NoticeType.WARNING, "REQUIRED")
                .write("\n\n$L", previousText);
    }
Adds nullability information to member docs.
smithy-docgen/src/main/java/software/amazon/smithy/docgen/interceptors/NullabilityInterceptor.java