src/vs/workbench/contrib/notebook/browser/view/notebookCellList.ts/NotebookCellList/setFocus
class NotebookCellList:	override setFocus(indexes: number[], browserEvent?: UIEvent, ignoreTextModelUpdate?: boolean): void {
		if (ignoreTextModelUpdate) {
			super.setFocus(indexes, browserEvent);
			return;
		}

		if (!indexes.length) {
			if (this._viewModel) {
				this._viewModel.updateSelectionsState({
					kind: SelectionStateType.Handle,
					primary: null,
					selections: []
				}, 'view');
			}
		} else {
			if (this._viewModel) {
				const focusedElementHandle = this.element(indexes[0]).handle;
				this._viewModel.updateSelectionsState({
					kind: SelectionStateType.Handle,
					primary: focusedElementHandle,
					selections: this.getSelection().map(selection => this.element(selection).handle)
				}, 'view');
			}
		}

		super.setFocus(indexes, browserEvent);
	}