code: @SafeVarargs
      public static <T> Set<T> unmodifiableSet(T... elements) {
          return Collections.unmodifiableSet(newHashSet(elements));
      }
docs: Creates a new unmodifiable {@code HashSet} containing all elements from {@code elements}.
  
  @param elements the elements that the set should contain, must not be {@literal null}.
  @param <T> the element type
  @return a new {@code HashSet} containing all elements from {@code elements}.