src/vs/workbench/contrib/notebook/browser/view/renderers/markdownCell.ts/StatefulMarkdownCell/setFoldingIndicator
class StatefulMarkdownCell:	setFoldingIndicator() {
		switch (this.foldingState) {
			case CellFoldingState.None:
				this.templateData.foldingIndicator.innerText = '';
				break;
			case CellFoldingState.Collapsed:
				DOM.reset(this.templateData.foldingIndicator, renderIcon(collapsedIcon));
				break;
			case CellFoldingState.Expanded:
				DOM.reset(this.templateData.foldingIndicator, renderIcon(expandedIcon));
				break;

			default:
				break;
		}
	}