如何在QWEB报告中求和行(Odoo 13)？

<table class="table table-condensed">
    <thead>
        <tr>
            <th>字段1</th>
            <th>字段2</th>
            <th>字段3</th>
        </tr>
    </thead>
    <tbody>
        <tr t-foreach="records" t-as="record">
            <td><span t-esc="record.field1"/></td>
            <td><span t-esc="record.field2"/></td>
            <td><span t-esc="record.field3"/></td>
            <t t-set="total" t-value="total + record.field3"/>
        </tr>
        <tr>
            <td colspan="2">总计</td>
            <td><span t-esc="total"/></td>
        </tr>
    </tbody>
</table>