How to add a CSS class to a v3 widget?

In v2 of Filament, I have a blade file in resources/views/filament/widgets ... the very first line was

<x-filament::widget class="my-css-class-name">

<x-filament::widget class="my-css-class-name">

. I saw in the "Upgrading from v2.x" documentation that has now changed to

<x-filament-widgets::widget>

<x-filament-widgets::widget>

. I made that change but

my-css-class-name

my-css-class-name

is not being added to the generated HTML. How do I do that now?