StreamClass.dedup<S>(source: Source<S>): StreamClass<Exclude<S, AnyFailure>, Extract<S, AnyFailure>>
StreamClass#dedup as a static: Stream.dedup(source, …) is
Stream.from(source).dedup(…).
await Stream.dedup([1, 1, 2, 1]).collect(); // [1, 2, 1]
StreamClass<Exclude<S, AnyFailure>, Extract<S, AnyFailure>>