`<td t-att-style="'width:30%;' if is_stressed else 'width:25%;'"> <b> Sales </b> </td>`

i am converting this to 

​<td t-if="is_stressed" style="width:30%;"> <b> Sales </b> </td> 

<td t-elif="not is_stressed" style="width:25%;"> <b> Sales </b> </td>​

but its saying i cannot use owl directives in arch xml view

how to correct this?