我在上使用此代码single.php, 此查询工作正常，但当post有父项（父项也有子项）时，这会给出输出all posts of parent & children

但在这种情况下，我希望它只查询父术语帖子。

<?php 
$post_terms = wp_get_object_terms($post->ID, \'serial\', array(\'fields\'=>\'ids\'));
    $args = array(
        \'post_type\' => \'post\',
        \'post_status\' => \'publish\',
        \'order\'    => \'ASC\',
        \'posts_per_page\' => -1,
        \'tax_query\' => array(
            array(
                \'taxonomy\' => \'serial\',
                \'field\' => \'id\',
                \'terms\' => $post_terms,
                ),
        )
    );
    $the_query = new WP_Query( $args );
    if ( $the_query->have_posts() ) {
        while ( $the_query->have_posts() ) {
        $the_query->the_post();
            the_title();
        }
    } else {
    }
wp_reset_postdata();
?>

如何根据附加条款查询帖子，仅根据附加条款（当帖子有父条款时不检查子条款）？