docs: private static SXSSFWorkbook toSXSSFBook(Workbook book) {
  		if(book instanceof SXSSFWorkbook) {
  			return (SXSSFWorkbook) book;
  		}
  		if(book instanceof XSSFWorkbook) {
  			return new SXSSFWorkbook((XSSFWorkbook) book);
  		}
  		throw new POIException("The input is not a [xlsx] format.");
  	}