namespace System.Collections.Generic
{
    [DefaultMember("Item")]
    public class OrderedDictionary<TKey, TValue> : ICollection<KeyValuePair<TKey, TValue>>, IDictionary<TKey, TValue>, IEnumerable, IEnumerable<KeyValuePair<TKey, TValue>>, IList<KeyValuePair<TKey, TValue>>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, IReadOnlyDictionary<TKey, TValue>, IReadOnlyList<KeyValuePair<TKey, TValue>>, ICollection, IDictionary, IList
        where TKey, notnull
    {
        public sealed class KeyCollection : ICollection<TKey>, IEnumerable, IEnumerable<TKey>, IList<TKey>, IReadOnlyCollection<TKey>, IReadOnlyList<TKey>, ICollection, IList
        {
            public bool Contains(TKey key);
        }
    }
}