Добавяне на номерация на редовете в документ, оферта, поръчка, фактура и т.н.

<table class="table table-condensed">
                <thead style="background-color: #aaa;">
                    <tr>
                        <th>№</th>
                        <th>Description</th>
                        <th>Quantity</th>
                        <th class="text-right">Unit Price</th>
                        <th class="text-right" groups="sale.group_discount_per_so_line">Discount (%)</th>
                   
                        <th class="text-right">Amount</th>
                    </tr>
                </thead>
                <tbody class="invoice_tbody">
                    <tr t-foreach="o.invoice_line" t-as="l">
                      <td><span t-esc="l_index + 1"/></td>
                        <td><span t-field="l.name"/></td>
                        <td>
                            <span t-field="l.quantity"/>
                            <span t-field="l.uos_id" groups="product.group_uom"/>
                        </td>
                        <td class="text-right">
                            <span t-field="l.price_unit"/>
                        </td>
                        <td class="text-right" groups="sale.group_discount_per_so_line"><span t-field="l.discount"/></td>
                        
                        <td class="text-right">
                            <span t-field="l.price_subtotal" t-field-options="{&quot;widget&quot;: &quot;monetary&quot;, &quot;display_currency&quot;: &quot;o.currency_id&quot;}"/>
                        </td>
                    </tr>
                </tbody>
            </table>