src/vs/workbench/contrib/notebook/common/services/notebookSimpleWorker.ts/MirrorNotebookDocument/_spliceNotebookCells
class MirrorNotebookDocument:	_spliceNotebookCells(splices: NotebookCellTextModelSplice<IMainCellDto>[]) {
		splices.reverse().forEach(splice => {
			const cellDtos = splice[2];
			const newCells = cellDtos.map(cell => {
				return new MirrorCell(
					(cell as unknown as IMainCellDto).handle,
					cell.source,
					cell.language,
					cell.cellKind,
					cell.outputs,
					cell.metadata
				);
			});

			this.cells.splice(splice[0], splice[1], ...newCells);
		});
	}