/// <summary>
 /// Returns a <code>Set</code> such that each element in the returned set
 /// is a unique object e' that .equals the corresponding element e in the
 /// original set.
 /// </summary>
 public virtual ICollection <T> InternAll(ICollection <T> s)
 {
     lock (mutex)
     {
         return(delegate_.InternAll(s));
     }
 }