获取当前分类相关的标签内容

比方说分类是product. 标签是car, machine, 在product分类页面获取到当前分类所有文章的标签：

$related_tags = get_terms(array(
                            'taxonomy'   => 'product_archive',
                            'hide_empty' => true,
                            'object_ids' => get_posts(array(
                                'post_type'   => 'product',
                                'fields'      => 'ids',
                                'tax_query'   => array(
                                    array(
                                        'taxonomy' => 'product_category',
                                        'field'    => 'term_id',
                                        'terms'    => $current_term->term_id,
                                    ),
                                ),
                            )),
                        ));