private DiscreteCellSink(DiscreteCellStreamSink <T> streamSink, Cell <T> cell)
     : base(cell) => this.StreamSink = streamSink;
 private DiscreteCellSink(DiscreteCellStreamSink <T> streamSink, T initialValue)
     : this(streamSink, new Cell <T>(streamSink, initialValue))
 {
 }