src/vs/editor/contrib/documentSymbols/browser/outlineModel.ts/OutlineModel/merge
class OutlineModel:	merge(other: OutlineModel): boolean {
		if (this.uri.toString() !== other.uri.toString()) {
			return false;
		}
		if (this._groups.size !== other._groups.size) {
			return false;
		}
		this._groups = other._groups;
		this.children = other.children;
		return true;
	}