laravel pulling data from database

I'm still trying to wrap my head around whereHas() method. My case is this. I want to pull all users that belong to class

This is relations

Classes model

 public function users()
{
    return $this->belongsToMany('App\User')->withTimestamps();
}

User model

 public function classes()
{
    return $this->belongsToMany('App\Classes')->withTimestamps();
}

controller

 $class_us = User::whereHas('classes', function ($query) {
            $query->where('class',1);
        })->get();

When I do dd($class_us) i get an empty collection

via Chebli Mohamed