Check if entity is reacted by given user

[Petar]

public function isReactedBy($responder = null)
{
    if (is_null($responder)) {
        $responder = auth()->user();
    }

    return $this->reactions()
        ->where('responder_id', $responder->id)
        ->where('responder_type', get_class($responder))->exists();

}