src/vs/base/browser/ui/list/listWidget.ts/TraitRenderer/renderElement
class TraitRenderer:	renderElement(element: T, index: number, templateData: ITraitTemplateData): void {
		const renderedElementIndex = this.renderedElements.findIndex(el => el.templateData === templateData);

		if (renderedElementIndex >= 0) {
			const rendered = this.renderedElements[renderedElementIndex];
			this.trait.unrender(templateData);
			rendered.index = index;
		} else {
			const rendered = { index, templateData };
			this.renderedElements.push(rendered);
		}

		this.trait.renderIndex(index, templateData);
	}