throws IOException {
        final long firstKey = prepareRequests(request, response, params, timeout);
        doSend(request);
        return firstKey;
    }

    /**
     * @param request
     * @param response
     * @param params
     * @param timeout
     * @param firstKey
     * @return
     * @throws IOException
     */

  @Override
  public @Nullable Comparator<? super K> comparator() {
    return delegate().comparator();
  }

  @Override
  @ParametricNullness
  public K firstKey() {
    return delegate().firstKey();
  }

  @Override
  public SortedMap<K, V> headMap(@ParametricNullness K toKey) {
    return delegate().headMap(toKey);
  }

  @Override
  @ParametricNullness
  public K lastKey() {

    }

    @Override
    public @Nullable Comparator<? super R> comparator() {
      return sortedBackingMap().comparator();
    }

    @Override
    public R firstKey() {
      return sortedBackingMap().firstKey();
    }

    @Override
    public R lastKey() {
      return sortedBackingMap().lastKey();
    }

    @Override
    public SortedMap<R, Map<C, V>> headMap(R toKey) {

  @Override
  public @Nullable Comparator<? super K> comparator() {
    return delegate().comparator();
  }

  @Override
  @ParametricNullness
  public K firstKey() {
    return delegate().firstKey();
  }

  @Override
  public SortedMap<K, V> headMap(@ParametricNullness K toKey) {
    return delegate().headMap(toKey);
  }

  @Override
  @ParametricNullness
  public K lastKey() {

    }

    @Override
    public @Nullable Comparator<? super R> comparator() {
      return sortedBackingMap().comparator();
    }

    @Override
    public R firstKey() {
      return sortedBackingMap().firstKey();
    }

    @Override
    public R lastKey() {
      return sortedBackingMap().lastKey();
    }

    @Override
    public SortedMap<R, Map<C, V>> headMap(R toKey) {

    public Comparator<? super K> comparator() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().comparator();
    }

    @Override
    public K firstKey() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().firstKey();
    }

    @Override
    public K lastKey() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().lastKey();
    }

  }

  @Override
  public @Nullable Entry<K, V> pollLastEntry() {
    return Iterators.pollNext(descendingEntryIterator());
  }

  @Override
  @ParametricNullness
  public K firstKey() {
    Entry<K, V> entry = firstEntry();
    if (entry == null) {
      throw new NoSuchElementException();
    } else {
      return entry.getKey();
    }
  }

  @Override
  @ParametricNullness

      return new TreeRow(rowKey, fromKey, upperBound);
    }

    @Override
    public C firstKey() {
      updateBackingRowMapField();
      if (backingRowMap == null) {
        throw new NoSuchElementException();
      }
      return ((SortedMap<C, V>) backingRowMap).firstKey();
    }

    @Override
    public C lastKey() {
      updateBackingRowMapField();

    return Iterables.<@Nullable Entry<K, V>>getFirst(entrySet(), null);
  }

  /**
   * A sensible definition of {@link #firstKey} in terms of {@code firstEntry}. If you override
   * {@code firstEntry}, you may wish to override {@code firstKey} to forward to this
   * implementation.
   */
  protected K standardFirstKey() {
    Entry<K, V> entry = firstEntry();
    if (entry == null) {

    return Iterables.<@Nullable Entry<K, V>>getFirst(entrySet(), null);
  }

  /**
   * A sensible definition of {@link #firstKey} in terms of {@code firstEntry}. If you override
   * {@code firstEntry}, you may wish to override {@code firstKey} to forward to this
   * implementation.
   */
  protected K standardFirstKey() {
    Entry<K, V> entry = firstEntry();
    if (entry == null) {