src/vs/base/browser/ui/tree/objectTree.ts/CompressibleRenderer/renderTwistie
class CompressibleRenderer:	renderTwistie?(element: T, twistieElement: HTMLElement): boolean {
		if (this.renderer.renderTwistie) {
			return this.renderer.renderTwistie(element, twistieElement);
		}
		return false;
	}