code: static OutputStream clearContent(InputStream workbook) {
          ByteArrayOutputStream xlsx = new ByteArrayOutputStream();
          
          try { clearContent(ConverterUtils.newWorkbook(workbook)).write(xlsx); }
          catch (IOException e) { throw new CalculationEngineException(e); }
          
          return xlsx;
      }
docs: {@link #clearContent(Workbook)} with new {@link ConverterUtils#newWorkbook(InputStream)}.