Magento – How to add Create Print Label for Custom Shipping method in magento 2

I follow this document to create a custom shipping method, its works fine.

But I need to add Create Shipping Label functionality for this shipping method. I got these reference Link1 and Link2

They suggest Only UPS, USPS, FedEx, DHL these shipping method have functionality. I need to add my custom shipping method.

Suggest Me, how to add Create Shipping Label for our Custom Shipping method.

What I Did:

I have edit Magento\Shipping\Controller\Adminhtml\Order\ShipmentMassPrintShippingLabel to get custom shipping method details.

Then, I try to download shppinglabel for custom shipping method, but setting content not added in this file and also not supported this file.

        <?php
        /**
         *
         * Copyright © 2013-2017 Magento, Inc. All rights reserved.
         * See COPYING.txt for license details.
         */
        namespace Magento\Shipping\Controller\Adminhtml\Order\Shipment;
        use Magento\Backend\App\Action;
        use Magento\Framework\App\ResponseInterface;
        use Magento\Framework\App\Filesystem\DirectoryList;
        use Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection;
        use Magento\Ui\Component\MassAction\Filter;
        use Magento\Backend\App\Action\Context;
        use Magento\Shipping\Model\Shipping\LabelGenerator;
        use Magento\Framework\App\Response\Http\FileFactory;
        use Magento\Sales\Model\ResourceModel\Order\Shipment\CollectionFactory as ShipmentCollectionFactory;
        use Magento\Framework\Controller\ResultInterface;
        use Magento\Sales\Model\ResourceModel\Order\CollectionFactory;
        use Spipu\Html2Pdf\Html2Pdf;

        /**
         * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
         */
        class MassPrintShippingLabel extends \Magento\Sales\Controller\Adminhtml\Order\AbstractMassAction
        {
            /**
             * Authorization level of a basic admin session
             *
             * @see _isAllowed()
             */
            const ADMIN_RESOURCE = 'Magento_Sales::shipment';

            /**
             * @var LabelGenerator
             */
            protected $labelGenerator;

            /**
             * @var FileFactory
             */
            protected $fileFactory;

            /**
             * @var CollectionFactory
             */
            protected $collectionFactory;

            /**
             * @var ShipmentCollectionFactory
             */
            protected $shipmentCollectionFactory;

            protected $logger;
            protected $repositoryAddress;

            /**
             * @param Context $context
             * @param Filter $filter
             * @param CollectionFactory $collectionFactory
             * @param FileFactory $fileFactory
             * @param LabelGenerator $labelGenerator
             * @param ShipmentCollectionFactory $shipmentCollectionFactory
             */
            public function __construct(
                Context $context,
                Filter $filter,
                CollectionFactory $collectionFactory,
                FileFactory $fileFactory,
                LabelGenerator $labelGenerator,
                ShipmentCollectionFactory $shipmentCollectionFactory,
                \Psr\Log\LoggerInterface $logger,
                \Magento\Sales\Model\Order\AddressRepository $repositoryAddress

            ) {
                $this->fileFactory = $fileFactory;
                $this->collectionFactory = $collectionFactory;
                $this->shipmentCollectionFactory = $shipmentCollectionFactory;
                $this->labelGenerator = $labelGenerator;
                $this->logger =$logger;
                $this->repositoryAddress= $repositoryAddress;
                parent::__construct($context, $filter);
            }

            /**
             * Batch print shipping labels for whole shipments.
             * Push pdf document with shipping labels to user browser
             *
             * @param AbstractCollection $collection
             * @return ResponseInterface|ResultInterface
             */
            protected function massAction(AbstractCollection $collection)
            {
                $labelsContent = [];
                $shipments = $this->shipmentCollectionFactory->create()->setOrderFilter(['in' => $collection->getAllIds()]);

                if ($shipments->getSize()) {
                    /** @var \Magento\Sales\Model\Order\Shipment $shipment */
                    foreach ($shipments as $shipment) {
                        $labelContent = $shipment->getShippingLabel();
                        if ($labelContent) {
                            $labelsContent[] = $labelContent;
                        }
                    }
                }

                if (!empty($labelsContent)) {
                    $outputPdf = $this->labelGenerator->combineLabelsPdf($labelsContent);
                    return $this->fileFactory->create(
                        'ShippingLabels.pdf',
                        $outputPdf->render(),
                        DirectoryList::VAR_DIR,
                        'application/pdf'
                    );
                }else{

                    $collection_data = $collection->getData();
                    foreach($collection_data as $collect_data){
                        $shipping_address_id = $collect_data['shipping_address_id'];
                        $shipAddress = $this->repositoryAddress->get($shipping_address_id);
                        $shipping_info_array =[];
                        if($shipAddress->getId())
                        {
                            $shipping_info = $shipAddress->getData();
                            $firstname = $shipping_info['firstname'];
                            echo $lastname = $shipping_info['lastname'];
                            echo $street = $shipping_info['street'];
                            echo $city = $shipping_info['city'];
                            echo $postcode = $shipping_info['postcode'];
                            echo $region = $shipping_info['region'];
                            echo $country = $shipping_info['country_id'];
                            array_push($shipping_info_array, $firstname);
                            $outputPdf = $this->labelGenerator->combineLabelsPdf($labelsContent);
                            return $this->fileFactory->create(
                                'ShippingLabels.pdf',
                                $firstname,
                                DirectoryList::VAR_DIR,
                                'application/pdf'
                                );
                            $this->messageManager->addSuccess(__('Your are Choosed Custom Shipping Method'));
                        }
                    }



        //         $this->messageManager->addError(__('There are no shipping labels related to selected orders.'));
                return $this->resultRedirectFactory->create()->setPath('sales/order/');
            }
            }
        }

My code download file, but its not setting any content to this file.

Suggest me How to Set Custom values to this pdf file and download pdf file.