Any idea why Wordpress's inCategorgy tag is not working?

So I am trying to add a "-none" to a class for a post if it is in a specific category in Wordpress. So like lets say if I am viewing a post that has a category id of 7, i want a certain class titled "example" change to "example-none".

Here's my code:

<div class="example<?= is_category('events')  ?'-none':'' ?><?= in_category('7')   ?'-none':'' ?>">

The weird thing with the code is, it works in a page when I am viewing all the posts in a specific category. But when I go to an interior post that is in a specific category, the code does not work.

I am using the in_category('7') tag to achieve this on a wordpress sidebar.

Any idea on what I am doing wrong?

I would remove the quotes around the id of the category:

in_category(7)

This should be a number, not a string.

Thanks. i got it working using this code:

    <div class="example<? wp_reset_query(); ?><?= in_category(7)   ?'-none':'' ?>">