src/vs/editor/contrib/folding/browser/foldingModel.ts/FoldingModel/applyMemento
class FoldingModel:	public applyMemento(state: CollapseMemento) {
		if (!Array.isArray(state)) {
			return;
		}
		let toToogle: FoldingRegion[] = [];
		for (let range of state) {
			let region = this.getRegionAtLine(range.startLineNumber);
			if (region && !region.isCollapsed) {
				toToogle.push(region);
			}
		}
		this.toggleCollapseState(toToogle);
	}