}

    @Override
    public void remove() {
      valueIterator.remove();
      /*
       * requireNonNull is safe because we've already initialized `collection`. If we hadn't, then
       * valueIterator.remove() would have failed.
       */
      if (requireNonNull(collection).isEmpty()) {
        keyIterator.remove();
      }
      totalSize--;

    }

    @Override
    public void remove() {
      valueIterator.remove();
      /*
       * requireNonNull is safe because we've already initialized `collection`. If we hadn't, then
       * valueIterator.remove() would have failed.
       */
      if (requireNonNull(collection).isEmpty()) {
        keyIterator.remove();
      }
      totalSize--;