public function addTerm($term_id)
    {
        TermContainer::findOrFail($term_id);

        // Cancel if the user wants to add the same term again
        if ($this->getTaxonomyQuery()->where('term_id', $term_id)->count()) {
            return;
        }

        $this->taxonomies()->attach($term_id);

        Cache::forget($this->getTaxonomyCacheKey());
    }