<PackageReference Include="System.Reactive" Version="6.0.0" />

Pattern<TSource1, TSource2, TSource3, TSource4>

public class Pattern<TSource1, TSource2, TSource3, TSource4> : Pattern
public Pattern<TSource1, TSource2, TSource3, TSource4, TSource5> And<TSource5>(IObservable<TSource5> other)

public Plan<TResult> Then<TResult>(Func<TSource1, TSource2, TSource3, TSource4, TResult> selector)