docs: public static byte[] convertTextToOctetStream(Object source, MediaType sourceType) {
        if (source == null) return null;
        if (sourceType == null) {
           throw new NullPointerException("MediaType cannot be null!");
        }
        if (source instanceof byte[]) return (byte[]) source;
        return source.toString().getBytes(sourceType.getCharset());
     }