How to make a transition-group ?

I do have the following:
```vue
<silent-box :gallery="photos">
    <template #silentbox-item="{ silentboxItem }">
      <img :src="silentboxItem.src" />
	  ...
    </template>
</silent-box>
```

I'm not sure how to add `transition-group` to that kind of code. Tried it in pretty much any way without success.
Can you give me a tip for that one ? 😄 