code: static IDataSet toDataSet(final Workbook workbook) {
          Sheet sheet = workbook.getSheetAt(0); //TODO: this works only for single sheet documents
          DataSet dataSet = new DataSet(sheet.getSheetName());
          
          for (int i = sheet.getFirstRowNum(); i <= sheet.getLastRowNum(); i++) {
              IDsRow dsRow = dataSet.addRow();
              Row row = sheet.getRow(i);
              for (int j = row.getFirstCellNum(); j < row.getLastCellNum(); j++) {
                  Cell wbCell = row.getCell(j);
                  if (wbCell != null && wbCell.getCellType() == Cell.CELL_TYPE_FORMULA) {
                      throw new CalculationEngineException("DataSet should not contain formulas");
                  }
                  IDsCell cell = dsRow.addCell();
                  cell.setValue(ConverterUtils.resolveCellValue(wbCell));
              }
          }
          return dataSet;
      }
docs: Converts a {@link Workbook} to new {@link IDataSet}.
  Ignores empty rows.
  
  @throws {@link CalculationEngineException} if {@link Workbook} contains formulas or Cell references.