public final static ExpenseSheetDTO toDTO(ExpenseSheet expenseSheet) {
List<ExpenseSheetLineDTO> lineDTOs = new ArrayList<ExpenseSheetLineDTO>();
for (ExpenseSheetLine line : expenseSheet.getExpenseSheetLines()) {
lineDTOs.add(toDTO(line));
}
return new ExpenseSheetDTO(expenseSheet.getCode(),
expenseSheet.getDescription(), lineDTOs);
}