laravel model belong many code example

Example 1: how to use where relationship laravel

Event::with(["owner", "participants" => function($q) use($someId){
    $q->where('participants.IdUser', '=', 1);
    //$q->where('some other field', $someId);
}])

Example 2: laravel poly morphic relationship

class Mechanic extends Model
{
    /**
     * Get the car's owner.
     */
    public function carOwner()
    {
        return $this->hasOneThrough(
            'App\Owner',
            'App\Car',
            'mechanic_id', // Foreign key on cars table...
            'car_id', // Foreign key on owners table...
            'id', // Local key on mechanics table...
            'id' // Local key on cars table...
        );
    }
}