*/
    @CanIgnoreReturnValue
    @Override
    public Builder<E> addAll(Iterable<? extends E> elements) {
      checkNotNull(elements);
      if (hashTable != null) {
        for (E e : elements) {
          add(e);
        }
      } else {
        super.addAll(elements);
      }
      return this;
    }

    /**

      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    Builder<E> combine(Builder<E> builder) {
      contents.addAll(builder.contents);
      return this;
    }

    @Override
    public ImmutableSet<E> build() {
      return copyOf(contents.iterator());
    }
  }

     */
    @Override
    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterable<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @Override
    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue