src/vs/workbench/contrib/notebook/browser/contrib/cellStatusBar/notebookVisibleCellObserver.ts/NotebookVisibleCellObserver/constructor
class NotebookVisibleCellObserver:	constructor(private readonly _notebookEditor: INotebookEditor) {
		super();

		this._register(this._notebookEditor.onDidChangeVisibleRanges(this._updateVisibleCells, this));
		this._register(this._notebookEditor.onDidChangeModel(this._onModelChange, this));
		this._updateVisibleCells();
	}