public static bool AnyAt <TSource, TPredicate>(this ImmutableHashSet <TSource> source, TPredicate predicate = default)
     where TPredicate : struct, IFunction <TSource, int, bool>
 => ValueReadOnlyCollectionExtensions.AnyAt <ValueWrapper <TSource>, ImmutableHashSet <TSource> .Enumerator, TSource, TPredicate>(new ValueWrapper <TSource>(source), predicate);