<PackageReference Include="System.Reactive" Version="6.1.0-preview.9" />

System.Reactive.Linq.ObservableImpl.Timestamp<TSource>

sealed class Timestamp<TSource> : Producer<Timestamped<TSource>, _<TSource>>
namespace System.Reactive.Linq.ObservableImpl { } namespace System.Reactive.Linq.ObservableImpl { }