How to use the @theia/filesystem/lib/browser.FileStatNode.is function in @theia/filesystem

canHandle(element: object): number {
        const current = this.iconThemeService.getDefinition(this.iconThemeService.current);
        if (current instanceof PluginIconTheme && (
            (element instanceof URI && element.scheme === 'file') || URIIconReference.is(element) || FileStat.is(element) || FileStatNode.is(element)
        )) {
            return Number.MAX_SAFE_INTEGER;
        }
        return 0;
    }

protected getClassNames(element: URI | URIIconReference | FileStat | FileStatNode | WorkspaceRootNode): string[] {
        if (WorkspaceRootNode.is(element)) {
            const name = this.labelProvider.getName(element);
            if (element.expanded) {
                return [this.rootFolderExpandedIcon, this.expandedFolderNameIcon(name)];
            }
            return [this.rootFolderIcon, this.folderNameIcon(name)];
        }
        if (DirNode.is(element)) {
            if (element.expanded) {
                const name = this.labelProvider.getName(element);
                return [this.folderExpandedIcon, this.expandedFolderNameIcon(name)];
            }
            return this.getFolderClassNames(element);
        }
        if (FileStatNode.is(element)) {
            return this.getFileClassNames(element, element.fileStat.uri);
        }
        if (FileStat.is(element)) {
            if (element.isDirectory) {
                return this.getFolderClassNames(element);
            }
            return this.getFileClassNames(element, element.uri);
        }
        if (URIIconReference.is(element)) {
            if (element.id === 'folder') {
                return this.getFolderClassNames(element);
            }
            return this.getFileClassNames(element, element.uri && element.uri.toString());
        }
        return this.getFileClassNames(element, element.toString());
    }