get
Per-destination demand-shipment counter, or null if no transport time has been registered for sender. Counts individual demands shipped to sender via this carrier in the current replication.
Named DemandShipment (rather than Shipment) to disambiguate from TimeBasedLoadCarrier.getShipmentCounter, which counts load-level shipments at a different granularity. A load carrier overrides this to return its load-level counter, so the per-edge cost calculators read the right shipment count under formation.