Excluir subcategorias de um loop

function wpse_filter_child_cats( $query ) {

if ( $query->is_category ) {
$queried_object
= get_queried_object();
$child_cats
= (array) get_term_children( $queried_object->term_id, 'category' );

if ( ! $query->is_admin )
//exclude the posts in child categories
$query
->set( 'category__not_in', array_merge( $child_cats ) );
}

return $query;
}
add_filter
( 'pre_get_posts', 'wpse_filter_child_cats' );