docs: def get_entries(self, acc: Account, cls=AccountEntry) -> QuerySet:
          """
          Returns entries related to this invoice on specified account.
          :param acc: Account
          :param cls: AccountEntry class
          :return: QuerySet
          """
          return cls.objects.filter(Q(account=acc) & (Q(source_invoice=self) | Q(settled_invoice=self))) if acc else cls.objects.none()