silverstripe-cms/code/Model/SiteTreeFileExtension.php

<?php

namespace SilverStripe\CMS\Model;

use SilverStripe\Dev\Deprecation;
use SilverStripe\Assets\File;
use SilverStripe\ORM\DataExtension;
use SilverStripe\View\SSViewer;

/**
 * @deprecated 4.2.0 Use FileLinkTracking instead
 * @property File $owner
 */
class SiteTreeFileExtension extends DataExtension
{
    private static $casting = [
        'BackLinkHTMLList' => 'HTMLFragment'
    ];

    /**
     * Generate an HTML list which provides links to where a file is used.
     *
     * @return string
     */
    public function __construct()
    {
        Deprecation::notice('4.2.0', 'Use FileLinkTracking instead', Deprecation::SCOPE_CLASS);
    }

    public function BackLinkHTMLList()
    {
        $viewer = SSViewer::create(['type' => 'Includes', self::class . '_description']);
        return $viewer->process($this->owner);
    }
}