bbp_forum_query_topic_ids( int $forum_id )

function bbp_forum_query_topic_ids( $forum_id ) {
   	$topic_ids = bbp_get_public_child_ids( $forum_id, bbp_get_topic_post_type() );

	return apply_filters( 'bbp_forum_query_topic_ids', $topic_ids, $forum_id );
}