How to check if tags have been changed?

[digitall-it]

I am using this code to check if tags have changed on a model but it isn't working.

static::updating(function($hotel) {
    // if the tags are changed, we need to recalculate the ranking
    if ($hotel->relationLoaded('tags') && $hotel->tags->isDirty()) {
        CalculateHotelRank::dispatch($hotel);
    }
});

I get instead the error: Method Illuminate\Database\Eloquent\Collection::isDirty does not exist.