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public Map<Bank, List<Account>> findAllGroupByBank() {
     Map<Bank, List<Account>> result = new HashMap<>();
    
            this.accountService
                    .findAll()
                    .stream()
                    .forEach(a -> result.computeIfAbsent(a.getBank(), this::findAllByBank));
            return result;
   }

   private List<Account> findAllByBank(Bank aBank) {
       return this.accountService.findAll().stream().filter(account -> aBank.equals(account.getBank())).collect(Collectors.toList());
   }