def get_splits_up_to(self, date_to: datetime) -> List[Split]:
        """ returns splits only up to the given date """
        query = (
            self.book.session.query(Split)
            .join(Transaction)
            .filter(Split.account == self.account,
                    Transaction.post_date <= date_to.date())
        )
        return query.all()
returns splits only up to the given date