static void writeBytes(
            final CharSequence s, final OutputStream out) throws IOException {
        final ByteArrayBuffer b = encode(StandardCharsets.ISO_8859_1, s);
        writeBytes(b, out);
    }
The epilogue to be included after the multipart content.
httpclient5/src/main/java/org/apache/hc/client5/http/entity/mime/AbstractMultipartFormat.java