In my sales order invoice template I get only one variant attribute of a product.I want to print all variants of a product in my    invoice template.I  tried this below code in report_invoice_document

<t t-set="itr" t-value="0"/> 
      <tr t-foreach="o.invoice_line_ids" t-as="l">
             <t t-set="itr" t-value="itr+1"/>
             <td><t t-esc="itr"/></td>
             <td><span t-field="l.name"/>||<span t-field="l.product_id.product_variant_ids"/>
                    <span t-field="l.product_id.is_product_variant"/>||<span t-field="l.product_id.attribute_line_ids"/>||
                    <span t-field="l.product_id.attribute_value_ids"/></td>

[456] pants (Blue, Small)||product.product(2,)True||product.attribute.line(10, 11)||product.attribute.value(1, 4)