bbp_forum_query_subforum_ids( int $forum_id )

function bbp_forum_query_subforum_ids( $forum_id ) {
	$subforum_ids = bbp_get_all_child_ids( $forum_id, bbp_get_forum_post_type() );
	//usort( $subforum_ids, '_bbp_forum_query_usort_subforum_ids' );

	return apply_filters( 'bbp_get_forum_subforum_ids', $subforum_ids, $forum_id );
}