The trait use when we need function like Model::findOrFail(), but it used for slug. Or even the other field?

ModelSlug.php

namespace app\lib\ModelSlug;
/**
 * Imagine we have Category and Post, and we want to search for Post that are in Category, using a slug
 * of Category.
 * 
 * In controller ...
 *
 * $posts = Category::findSlugOrFail($theSlugFromRoute, $the_slug_field)->posts()->get(); 
 *
 * If failed, it will throw the same exception as findOrFail did.
 */
trait ModelSlug {

    public static function findSlugOrFail($slug, $slugField='slug') {
        
		if ( ! is_null($model = static::where($slugField, '=', $slug)->first())) return $model;

		throw with(new ModelNotFoundException)->setModel(get_called_class());
        
    }
}