Template source: submit_buttons.html

<div class="col-md-12 panel panel-primary">
    <div class="panel-body">
        {% for button_name, button in buttons.items %}
        <a href="#" class="btn btn-{{ button.color }} btn-lg btn-block has-spinner" onclick='document.getElementById("{{ form_id }}").submit()'>
           <span class="spinner"><i class="fa fa-spinner fa-spin"></i></span> {{ button.label }}
        </a>
        {% endfor %}
    </div>
</div>