reference
fun <SourceT : ITypedNode, TargetT : ITypedNode> reference(input: IMonoStep<SourceT>, link: ITypedReferenceLink<TargetT>): IMonoStep<TargetT>
fun <SourceT : ITypedNode, TargetT : ITypedNode> reference(input: IFluxStep<SourceT>, link: ITypedReferenceLink<TargetT>): IFluxStep<TargetT>