This filter allows you to add additional CSS classes to the outer div of the [wpsl] template.
So if you have multiple store locator pages, then you could use this to apply different styles without having to create a different template.
$classes - (array) The default CSS classes.
The code below shows how to set a ‘wpsl-custom-css’ class on a page with the ‘your-page-slug’ permalink.
This filter is located in /frontend/class-frontend.php
The code needs to be placed in the functions.php file inside your active theme folder.