[web2py] CSS on custom form widget.

[David]

I have

{{=form.custom.widget.name_on_card }}
which generates

<input type="text" value="Person name" name="name_on_card" 
id="no_table_name_on_card" class="string">


How do I add an additional class to the rendered output?

ie: big

<input type="text" value="Person name" name="name_on_card" 
id="no_table_name_on_card" class="string big">

Thanks.