docs: private static Object getCellValue(Cell cell) throws Exception {
          Object value = null;
          if (cell instanceof ErrorCell) {
              value = null;
          } else if (cell instanceof LabelCell) {
              value = ((LabelCell) cell).getString();
          } else if (cell instanceof NumberCell) {
              value = ((NumberCell) cell).getValue();
          } else if (cell instanceof DateCell) {
              value = ((DateCell) cell).getDate();
          } else if (cell instanceof BooleanCell) {
              value = ((BooleanCell) cell).getValue();
          } /*else if (cell instanceof FormulaCell) {
              value = ((FormulaCell) cell).getFormula();
          }*/ else {
              value = cell.getContents();
          }
          return value;
      }