public _(Take <TSource> parent, IObserver <TSource> observer, IDisposable cancel)
     : base(observer, cancel)
 {
     _parent    = parent;
     _remaining = _parent._count;
 }
 public TakeImpl(Take <TSource> parent, IObserver <TSource> observer, IDisposable cancel)
     : base(observer, cancel)
 {
     _parent = parent;
 }