protected function deleteLinked($field_value_id)
    {
        $this->db->delete('product_field', array('field_value_id' => $field_value_id));
        $this->db->delete('field_value_translation', array('field_value_id' => $field_value_id));
        $this->db->delete('file', array('entity' => 'field_value', 'entity_id' => $field_value_id));
    }