src/vs/workbench/api/common/extHostTypes.ts/NotebookCellData/isNotebookCellDataArray
class NotebookCellData:	static isNotebookCellDataArray(value: unknown): value is vscode.NotebookCellData[] {
		return Array.isArray(value) && (<unknown[]>value).every(elem => NotebookCellData.isNotebookCellData(elem));
	}