def _download_query(self, as_of):
c = self.institution.client()<EOL>q = c.credit_card_account_query(number=self.number, date=as_of)<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