namespace System.Collections.Generic
{
    [DebuggerDisplay("Count = {Count}")]
    [DebuggerTypeProxy(typeof(SortedSetDebugView<?>))]
    public class SortedSet<T> : ICollection<T>, IEnumerable<T>, ISet<T>, ICollection, IEnumerable, IDeserializationCallback, ISerializable
    {
        public bool IsProperSupersetOf(IEnumerable<T> other);
    }
}