src/vs/workbench/api/common/extHostTypes.ts/NotebookRange/isNotebookRange
class NotebookRange:	static isNotebookRange(thing: any): thing is vscode.NotebookRange {
		if (thing instanceof NotebookRange) {
			return true;
		}
		if (!thing) {
			return false;
		}
		return typeof (<NotebookRange>thing).start === 'number'
			&& typeof (<NotebookRange>thing).end === 'number';
	}