How does \Magento\Shipping\Controller\Adminhtml\Order\ShipmentLoader::load() work?

Development Shipment
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1

Context: How is «Submit Shipment» implemented?

958164/app/code/Magento/Shipping/Controller/Adminhtml/Order/ShipmentLoader.php#L95-L142

/**
 * Initialize shipment model instance
 *
 * @return bool|\Magento\Sales\Model\Order\Shipment
 * @throws \Magento\Framework\Exception\LocalizedException
 */
public function load()
{
	$shipment = false;
	$orderId = $this->getOrderId();
	$shipmentId = $this->getShipmentId();
	if ($shipmentId) {
		$shipment = $this->shipmentRepository->get($shipmentId);
	} elseif ($orderId) {
		$order = $this->orderRepository->get($orderId);

		/**
		 * Check order existing
		 */
		if (!$order->getId()) {
			$this->messageManager->addError(__('The order no longer exists.'));
			return false;
		}
		/**
		 * Check shipment is available to create separate from invoice
		 */
		if ($order->getForcedShipmentWithInvoice()) {
			$this->messageManager->addError(__('Cannot do shipment for the order separately from invoice.'));
			return false;
		}
		/**
		 * Check shipment create availability
		 */
		if (!$order->canShip()) {
			$this->messageManager->addError(__('Cannot do shipment for the order.'));
			return false;
		}

		$shipment = $this->shipmentFactory->create(
			$order,
			$this->getItemQtys(),
			$this->getTracking()
		);
	}

	$this->registry->register('current_shipment', $shipment);
	return $shipment;
}

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