src/vs/editor/common/model/editStack.ts/MultiModelEditStackElement/append
class MultiModelEditStackElement:	public append(model: ITextModel, textChanges: TextChange[], afterEOL: EndOfLineSequence, afterVersionId: number, afterCursorState: Selection[] | null): void {
		const key = uriGetComparisonKey(model.uri);
		const editStackElement = this._editStackElementsMap.get(key)!;
		editStackElement.append(model, textChanges, afterEOL, afterVersionId, afterCursorState);
	}