src/vs/workbench/contrib/notebook/browser/contrib/cellStatusBar/contributedStatusBarItemController.ts/ContributedStatusBarItemController/_updateEverything
class ContributedStatusBarItemController:	private _updateEverything(): void {
		const newCells = this._observer.visibleCells.filter(cell => !this._visibleCells.has(cell.handle));
		const visibleCellHandles = new Set(this._observer.visibleCells.map(item => item.handle));
		const currentCellHandles = Array.from(this._visibleCells.keys());
		const removedCells = currentCellHandles.filter(handle => !visibleCellHandles.has(handle));
		const itemsToUpdate = currentCellHandles.filter(handle => visibleCellHandles.has(handle));

		this._updateVisibleCells({ added: newCells, removed: removedCells.map(handle => ({ handle })) });
		itemsToUpdate.forEach(handle => this._visibleCells.get(handle)?.update());
	}