How to display product variant in report? - python-2.7

Question

I have create a custom module for sale order report . In my case, articles have attributes that have more then one value for example color: red, blue. I want to display in the article description the value of the variants. I tried several code but I did not get the right result either it displays all the value of an attribute.Any idea for help please?
report_saleorder.xml
<?xml version="1.0" encoding="utf-8"?>
<openerp>
<data> ...
<table class="table table-condensed" style="margin-top:25px;">
<thead>
<tr>
<th>N°</th>
<th>REFERENCE</th>
<th>DESCRIPTION</th>
<th class="text-left">QTE</th>
<th class="text-left">PRIX UHT</th>
<th t-if="display_discount" class="text-left"
groups="sale.group_discount_per_so_line">
REMISE (%)
</th>
<th>TOTAL NET HT</th>
<th class="text-left">TVA</th>
</tr>
</thead>
<tbody class="sale_tbody">
<t t-foreach="doc.order_line" t-as="l">
<tr t-if="l.product_uom_qty">
<td>
<span t-esc="str(l_index+1)"/>
</td>
<td>
<span t-field="l.product_id.default_code"/>
</td>
<span t-field="value.name"/>
<td style="width:50%;">
[<span t-field="l.product_id.name"/>]
<br/>
<t t-foreach="l.product_id.attribute_line_ids" t-as="variant">
<!-- - -->
<strong><span t-field="variant.attribute_id"/>:
</strong>
<t t-foreach="variant.value_ids" t-as="value">
<!--<span t-field="variant.value_ids.name"/>-->
<span t-field="value.name"/>
<!--<br/>-->
</t>
</t>
<span t-field="l.product_id.description_sale"/>
<td class="text-left" style="width:7%;">
<span t-esc="'%.f'%(l.product_uom_qty)"/>
<!--<span groups="product.group_uom" t-field="l.product_uom"/>-->
</td>
<td class="text-left" style="width:12%;">
<span t-field="l.price_unit"/>
</td>
<td t-if="display_discount" class="text-left"
groups="sale.group_discount_per_so_line" style="width:11%;">
<span t-esc="'%.f'%(l.discount)"/>
</td>
<td style="width:15%;">
<span t-field="l.price_subtotal"/>
</td>
<td class="text-left" style="width:9%">
<span t-esc="', '.join(map(lambda x: (x.description or x.name), l.tax_id))"/>
</td>
</tr>
</t>
</tbody>
</table>

Answer 1

This question is similar and somehow a duplicate of:
(odoo10) how to add product attributes in pdf invoice
See how to do it there