src/vs/workbench/contrib/notebook/browser/viewModel/baseCellViewModel.ts/BaseCellViewModel/updateEditState
class BaseCellViewModel:	updateEditState(newState: CellEditState, source: string) {
		this._editStateSource = source;
		if (newState === this._editState) {
			return;
		}

		this._editState = newState;
		this._onDidChangeState.fire({ editStateChanged: true });
		if (this._editState === CellEditState.Preview) {
			this.focusMode = CellFocusMode.Container;
		}
	}