+sub shipped_qty {
+ my ($self) = @_;
+
+ my $d_orders = $self->order->linked_records(direction => 'to', to => 'SL::DB::DeliveryOrder');
+ my @doi = grep { $_->parts_id == $self->parts_id } map { $_->orderitems } @$d_orders;
+
+ return sum(map { AM->convert_unit($_->unit => $self->unit) * $_->qty } @doi);
+}
+