public function localizableLocales()
    {
        // Keep only locales that don't exist in ...
        return array_diff_key(
            Config::get('decoy.site.locales'),

            // ... the locales of other localizations ...
            $this->other()->pluck('locale')->flip()->toArray(),

            // ... and the model's locale
            [$this->item->locale => null]
        );
    }