Django loop – remove last comma

What about this?

{% for product_in_series in series.get_products %}{%spaceless%}
    {% with product_in_series.product as product %}
    {%if not forloop.first%}
        "<img src='{% version product.get_overview 'page_image' %}'>"
        {%if not forloop.last%},{%endif%}
    {%endif%}
    {% endwith %}
{%endspaceless%}{% endfor %}

{{ forloop.last|yesno:",,"|safe }}

, - is a comma