public static Task AppendToStream(
     this IEventStore eventStore,
     string streamId,
     int expectedVersion,
     NewStreamEvent newStreamEvent)
 {
     return eventStore.AppendToStream(streamId, expectedVersion, new[] { newStreamEvent });
 }
 public static Task AppendToStream(
     this IEventStore eventStore,
     string streamId,
     int expectedVersion,
     IEnumerable<NewStreamEvent> events)
 {
     return eventStore.AppendToStream(streamId, expectedVersion, events);
 }