protected function deleteLinked($category_id)
    {
        $this->db->delete('category_translation', array('category_id' => $category_id));
        $this->db->delete('file', array('entity' => 'category', 'entity_id' => $category_id));
        $this->db->delete('alias', array('entity' => 'category', 'entity_id' => $category_id));
    }