Print format Jinja problem


Why am i getting a error for this?
How do i get the rate?
This is the code:

<table class="table table-condensed cart no-border">
	<thead>
		<tr>
		    <th width="20%" class="text-right">{{ _("Item Name") }}</th>
			<th width="20%" class="text-right">{{ _("Sqm_ft") }}</th>
            <th width="20%" class="text-right">{{ _("Rate") }}</th>
			<th width="30%" class="text-right">{{ _("Amount") }}</th>
		</tr>
	</thead>
	<tbody>
<table>

<tbody>
<!-- group items by item_code //-->
{% for item, item_group in doc.items|groupby('item_group') %}
	<tr>
	    <td>{{item}}</td>
		<!-- get group total //-->
		<td>{{item_group|sum(attribute='qty') }}</td>
		<td>{{item_group|format(attribute='rate') }}</td>
		<td>{{item_group|sum(attribute='amount')}}</td>
	</tr>

{%- endfor -%}
</tbody>

</table>

{{ no such element: list object[‘rate’] }}
and
jinja2.exceptions.UndefinedError: ‘erpnext.selling.doctype.sales_order_item.sales_order_item.SalesOrderItem object’ has no attribute ‘Rate’