sub paths 
{
    my $paths_ref = shift;

    while ( my ($k,$v) = each %$paths_ref) {
        my $l=$root->lookup($k);
        if ($l->is_container) {
            if ($l->has_children) {
                foreach my $c($l->children) {
                    my $c_ref = {};
                    $paths_ref->{$c} = $c_ref;
                    paths($paths_ref->{$c});
                }
            } else {
                $paths_ref->{$k} = undef;
            }
        } else {
            $paths_ref->{$k} = undef;
        }
    }
}