package MyModel;
use strict;
use warnings;
use Gtk2;

use Glib::Object::Subclass
  Glib::Object::,
  interfaces => [ Gtk2::TreeModel:: ];

sub ITER_NTH_CHILD {
  my ($self, $iter, $n) = @_;
  my $ref = [ 123 ];
  return [ 999, 0, $ref, undef ];
}

package main;
use strict;
use warnings;
use Gtk2;
my $model = MyModel->new;

my $iter = $model->iter_nth_child (undef, 5);
$iter->to_arrayref(999);