the below functino calls the pos reciepet report, it does the call but the report is missing some fuctions in its parser file. is there a way to include the default parser with my script

@api.one    
def print_report(self):
        report_obj = self.env['report']
        report = report_obj._get_report_from_name('point_of_sale.report_receipt')
        docargs = {
            'doc_ids': self.pos_order.id,
            'doc_model': report.model,
            'docs': self.pos_order,
        }
        return report_obj.render('point_of_sale.report_receipt', docargs)