def _download_query(self, as_of):
c = self.institution.client()<EOL>q = c.brokerage_account_query(<EOL>number=self.number, date=as_of, broker_id=self.broker_id)<EOL>return q<EOL>
Formulate the specific query needed for download

        Not intended to be called by developers directly.

        :param as_of: Date in 'YYYYMMDD' format
        :type as_of: string