scope 搞不懂了. 帮我分析一下呗?

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use App\Filters\ThreadsFilters;
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public function index(Channel $channel,ThreadsFilters $filters)
{
    if ($channel->exists) {
        $threads = $channel->threads()->latest();
    } else {
        $threads = Thread::latest();
    }

    $threads = $threads->filter($filters)->get();

    return view('threads.index',compact('threads'));
}
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这里的 $threads = $threads->filter($filters)->get();, 其中 $filters 是一个实例, 我不理解了. 手册上也没有讲解. 怎么理解?