public Map<R, V> column(C columnKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.column(columnKey);
    }

    @Override
    public Set<C> columnKeySet() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.columnKeySet();
    }

    @Override
    public Map<C, Map<R, V>> columnMap() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.columnMap();
    }

    delegate().clear();
  }

  @Override
  public Map<R, V> column(@ParametricNullness C columnKey) {
    return delegate().column(columnKey);
  }

  @Override
  public Set<C> columnKeySet() {
    return delegate().columnKeySet();
  }

  @Override
  public Map<C, Map<R, V>> columnMap() {
    return delegate().columnMap();
  }

  @Override

    Table<String, Integer, Character> transpose = transpose(original);
    original.put(1, "foo", 'a');
    assertSame(original.columnKeySet(), transpose.rowKeySet());
    assertSame(original.rowKeySet(), transpose.columnKeySet());
    assertSame(original.columnMap(), transpose.rowMap());
    assertSame(original.rowMap(), transpose.columnMap());
    assertSame(original.values(), transpose.values());

    public Map<R, V> column(C columnKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.column(columnKey);
    }

    @Override
    public Set<C> columnKeySet() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.columnKeySet();
    }

    @Override
    public Map<C, Map<R, V>> columnMap() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.columnMap();
    }

  }

  public void testColumn() {
    assertEquals(ImmutableMap.of(), INSTANCE.column(1));
  }

  public void testColumnKeySet() {
    assertEquals(ImmutableSet.of(), INSTANCE.columnKeySet());
  }

  public void testColumnMap() {
    assertEquals(ImmutableMap.of(), INSTANCE.columnMap());
  }

  public void testContains() {
    assertFalse(INSTANCE.contains('a', 1));
  }

    assertEquals(ImmutableMap.of(), testTable.column(0));
    assertEquals(ImmutableMap.of('a', "blah"), testTable.column(1));
  }

  public void testColumnKeySet() {
    assertEquals(ImmutableSet.of(1), testTable.columnKeySet());
  }

  public void testColumnMap() {
    assertEquals(ImmutableMap.of(1, ImmutableMap.of('a', "blah")), testTable.columnMap());
  }

  public void testRow() {

  }

  public void testColumnSetPartialOverlap() {
    table = create("foo", 1, 'a', "bar", 1, 'b', "foo", 2, 'c', "bar", 3, 'd');
    assertThat(table.columnKeySet()).containsExactly(1, 2, 3);
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointerInstance() {

    }
  }

  public void testColumnKeySet() {
    for (ImmutableTable<Character, Integer, String> testInstance : getTestInstances()) {
      assertEquals(ImmutableSet.of(1, 2), testInstance.columnKeySet());
    }
  }

  public void testColumnMap() {
    for (ImmutableTable<Character, Integer, String> testInstance : getTestInstances()) {
      assertEquals(
          ImmutableMap.of(

  }

  @Override
  @J2ktIncompatible // serialization
  @GwtIncompatible // serialization
  Object writeReplace() {
    Map<C, Integer> columnKeyToIndex = Maps.indexMap(columnKeySet());
    int[] cellColumnIndices = new int[cellSet().size()];
    int i = 0;
    for (Cell<R, C, V> cell : cellSet()) {
      // requireNonNull is safe because the cell exists in the table.

  }

  @Override
  @J2ktIncompatible // serialization
  @GwtIncompatible // serialization
  Object writeReplace() {
    Map<C, Integer> columnKeyToIndex = Maps.indexMap(columnKeySet());
    int[] cellColumnIndices = new int[cellSet().size()];
    int i = 0;
    for (Cell<R, C, V> cell : cellSet()) {
      // requireNonNull is safe because the cell exists in the table.