And just for completeness, here is an example using iter_next. One could argue that the lack of callbacks make this somewhat easier to read than the foreach example.

my $iter = $model->get_iter_first();
while ($iter) {
    my @selected = $labels_model->get( $iter );
    print @selected;
    $iter = $model->iter_next( $iter );
}
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See also the more detailed foreach example by kikuchiyo in 11104587.