public static Option <TSource> Single <TSource>(this ImmutableStack <TSource> source)
#pragma warning disable HLQ005 // Avoid Single() and SingleOrDefault()
        => ValueEnumerableExtensions.Single <ValueWrapper <TSource>, ValueWrapper <TSource> .Enumerator, TSource>(new ValueWrapper <TSource>(source));
 public static Option <TSource> Single <TSource>(this ImmutableQueue <TSource> source)
 => ValueEnumerableExtensions.Single <ValueWrapper <TSource>, ValueWrapper <TSource> .Enumerator, TSource>(new ValueWrapper <TSource>(source));