Hi,

I am creating a new report via XML in a module

 <report
            id="report_invoice_custom"
            model="account.invoice"
            string="Custom invoice report"
            report_type="qweb-pdf"
            name="custom_invoice_report.invoice_custom"
            attachment_use="False"
            file="custom_invoice_report.invoice_custom"
                attachment = "(object.state in ('open','paid')) and ('F_'+(object.number or '').replace('/','')+'.pdf')"
                paperformat_id = "1" <-- THIS DOES NOT WORK!
        />

paperformat_id is not a field of report but it has to be specified through relationship report.paperformat.

How could be specified such relationship through XML?