I want to add custom css class to view, but only for users in some group.

    <template id="customCss" inherit_id="web.webclient_bootstrap" name="add css class">

<xpath expr="//header" position="attributes">
   <attribute name="groups">my_module.custom_group</attribute>

// Here instead of showing to only custom group, i want to add css class for that group

</xpath>

</template>