first（）和take（）在Eager Load laravel中无法正常工作

I have a Post Model that have a hasMany relation to post_pics and belongsToMany relation to Category Model.

I want to fetch All Posts and All their Categories but First post_pics of each Post.

For that I write this Eager Load Constraints :

Post::with([
                'post_pics'  => function ($query) {
                    $query->select(['pic_id', 'pic_name', 'post_id'])->first()->get();
                },
                'categories' => function ($query) {
                    $query->select(['categories.cat_id', 'name']);
                }
            ])
                ->take(12)->orderBy('created_at', 'desc')
                ->get(['post_id', 'post_title', 'post_alias', 'post_content', 'comments_count', 'created_at']);

        return $latestPosts;

When I remove first() method after select() method all things works and returns all pictures of each Post but when I use first() method, only returns first picture of Models that have more than one picture.

I try to take(1) Constraints but it does not work too.

What is Problem and How Can I do that?