* @throws NullPointerException if {@code elements} is null or contains a null element
     */
    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterator<? extends E> elements) {
      while (elements.hasNext()) {
        add(elements.next());
      }
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableCollection} of the appropriate type, containing the

     * @throws NullPointerException if {@code elements} is null or contains a null element
     */
    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterator<? extends E> elements) {
      while (elements.hasNext()) {
        add(elements.next());
      }
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableCollection} of the appropriate type, containing the