<ul t-if="category.child_id" class="nav nav-pills nav-stacked nav-hierarchy">
<t t-foreach="category.child_id" t-as="category">
<t t-call="website_sale.categories_recursive"/>
<ul t-if="category.child_id" class="nav nav-pills nav-stacked nav-hierarchy">
<t t-foreach="category.child_id" t-as="category">
<t t-call="website_sale.categories_recursive"/>