docs: public static boolean isXlsx(InputStream in) {
  		if (false == in.markSupported()) {
  			in = new BufferedInputStream(in);
  		}
  		try {
  			return FileMagic.valueOf(in) == FileMagic.OOXML;
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		}
  	}