def transactions(self) -> TransactionsAggregate:
        """ Transactions aggregate """
        if not self.__transactions_aggregate:
            self.__transactions_aggregate = TransactionsAggregate(self.book)
        return self.__transactions_aggregate
def transactions ( self ) -> TransactionsAggregate : if not self . __transactions_aggregate : self . __transactions_aggregate = TransactionsAggregate ( self . book ) return self . __transactions_aggregate
Transactions aggregate