I'm trying to generate a report like described in https://www.odoo.com/documentation/11.0/howtos/backend.html#reporting

    <report
        id="report_session"
        model="custom_module.voiture"
        string="Session Report"
        name="custom_module.report_session_view"
        file="custom_module.report_session"
        report_type="qweb-html" />
    
    <template id="report_session_view">
        <t t-call="web.html_container">
            <t t-call="web.external_layout">
            	<t t-foreach="docs" t-as="doc">
                    <div class="page">
                        <h2 t-field="doc.name"/>
                        <p>Test</p>
                    </div>
                </t>
            </t>
        </t>
    </template>

The problem I have is that the variable docs, which is supposed to be a set of the records of custom_record.voiture is always empty even though records exist in the system