/// <summary>
 /// The Key.
 /// </summary>
 /// <typeparam name="V">.</typeparam>
 /// <param name="obj">The obj<see cref="IUnique{V}"/>.</param>
 /// <returns>The <see cref="UInt64"/>.</returns>
 public virtual UInt64 Key <V>(IUnique <V> obj)
 {
     return(obj.UniquesAsKey());
 }
 /// <summary>
 /// The Key.
 /// </summary>
 /// <typeparam name="V">.</typeparam>
 /// <param name="obj">The obj<see cref="IUnique{V}"/>.</param>
 /// <returns>The <see cref="UInt64"/>.</returns>
 public override UInt64 Key <V>(IUnique <V> obj)
 {
     return(obj.UniquesAsKey());
 }