pms/pms/report/proforma_report_templates.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>

    <template id="report_pms_pro_forma">
        <t t-call="web.html_container">
            <t t-foreach="docs" t-as="o">
                <t t-set="is_pro_forma" t-value="True" />
                <t t-set="o" t-value="o.with_context(proforma=True)" />
                <t
                    t-call="account.report_invoice_document"
                    t-lang="o.partner_id.lang"
                />
            </t>
        </t>
    </template>

</odoo>