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) {

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

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

    @Override
    @ParametricNullness
    public K lastKey() {
      return sortedMap().lastKey();
    }

    @Override

      return new StandardNavigableKeySet();
    }

    @Override
    public NavigableSet<K> descendingKeySet() {
      return standardDescendingKeySet();
    }

    @Override
    public K firstKey() {
      return standardFirstKey();
    }

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

    @Override
    public K lastKey() {

      return new StandardNavigableKeySet();
    }

    @Override
    public NavigableSet<K> descendingKeySet() {
      return standardDescendingKeySet();
    }

    @Override
    public K firstKey() {
      return standardFirstKey();
    }

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

    @Override
    public K lastKey() {

  }

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

  @Override
  public @Nullable K firstKey() {
    return sortedDelegate.firstKey();
  }

  @Override
  public @Nullable K lastKey() {
    return sortedDelegate.lastKey();
  }

  @Nullable K higher(K k) {

  }

  public void testRowMapFirstKey() {
    sortedTable = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    assertSame("bar", sortedTable.rowMap().firstKey());
  }

  public void testRowMapLastKey() {
    sortedTable = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    assertSame("foo", sortedTable.rowMap().lastKey());
  }

    TreeMultimap<String, Integer> multimap = createPopulate();
    SortedMap<String, Collection<Integer>> asMap = multimap.asMap();
    assertEquals(Ordering.natural(), asMap.comparator());
    assertEquals("foo", asMap.firstKey());
    assertEquals("tree", asMap.lastKey());
    Set<Integer> fooValues = ImmutableSet.of(1, 3, 7);
    Set<Integer> googleValues = ImmutableSet.of(2, 6);
    Set<Integer> treeValues = ImmutableSet.of(4, 0);

      replica.put(newValue, new AtomicInteger(1));
    }
  }

  private static void removeMinFromReplica(
      SortedMap<Integer, AtomicInteger> replica, int minValue) {
    Integer replicatedMinValue = replica.firstKey();
    assertEquals(replicatedMinValue, (Integer) minValue);
    removeFromReplica(replica, replicatedMinValue);
  }

  private static void removeMaxFromReplica(