src/vs/workbench/contrib/notebook/browser/viewModel/baseCellViewModel.ts/BaseCellViewModel/_addCellDecoration
class BaseCellViewModel:	private _addCellDecoration(options: INotebookCellDecorationOptions): string {
		const id = ++this._lastDecorationId;
		const decorationId = `_cell_${this.id};${id}`;
		this._resolvedCellDecorations.set(decorationId, options);
		this._cellDecorationsChanged.fire({ added: [options], removed: [] });
		return decorationId;
	}