}

    @Override
    public void remove() {
      iterator.remove();
    }
  }

  @Nullable Set<K> keySet = null;

  @Override
  public Set<K> keySet() {
    // does not impact recency ordering
    Set<K> ks = keySet;
    return (ks != null) ? ks : (keySet = new KeySet(this));
  }

  @Nullable Collection<V> values = null;

  @Override
  public Collection<V> values() {

   * interface.
   *
   * @since 14.0 (present with return type {@code SortedSet} since 2.0)
   */
  @Override
  public NavigableSet<K> keySet() {
    return (NavigableSet<K>) super.keySet();
  }

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code TreeMultimap} has unique sorted keys, this method returns a {@link

      String value2 = key2.toString();
      assertThat(cache.getUnchecked(key1)).isSameInstanceAs(value1);
      assertThat(cache.getUnchecked(key2)).isSameInstanceAs(value2);
      assertThat(cache.asMap().keySet()).isEqualTo(ImmutableSet.of(key1, key2));
      assertThat(cache.asMap().values()).containsExactly(value1, value2);
      assertThat(cache.asMap().entrySet())

                        ArrayTable.create(rowKeys, columnKeys);
                    populateForRowKeySet(table, elements);
                    return table.column(1).keySet();
                  }
                })
            .named("ArrayTable.column.keySet")
            .withFeatures(
                CollectionSize.ONE,
                CollectionSize.SEVERAL,
                CollectionFeature.KNOWN_ORDER,

                        ArrayTable.create(rowKeys, columnKeys);
                    populateForRowKeySet(table, elements);
                    return table.column(1).keySet();
                  }
                })
            .named("ArrayTable.column.keySet")
            .withFeatures(
                CollectionSize.ONE,
                CollectionSize.SEVERAL,
                CollectionFeature.KNOWN_ORDER,

    }

    @LazyInit private transient @Nullable Set<K> keySet;

    @Override
    public Set<K> keySet() {
      Set<K> result = keySet;
      return (result == null) ? keySet = createKeySet() : result;
    }

    Set<K> createKeySet() {
      return new KeySet<>(this);
    }

    @LazyInit private transient @Nullable Collection<V> values;

          }
        }
        return endOfData();
      }
    }

    @Override
    Set<R> createKeySet() {
      return new KeySet();
    }

    @WeakOuter
    private final class KeySet extends Maps.KeySet<R, V> {
      KeySet() {
        super(Column.this);
      }

      @Override
      public boolean contains(@Nullable Object obj) {

    }
  }

  private transient @Nullable ImmutableSortedSet<K> keySet;

  @Override
  public ImmutableSortedSet<K> keySet() {
    ImmutableSortedSet<K> ks = keySet;
    return (ks == null) ? (keySet = createKeySet()) : ks;
  }

  @Override
  ImmutableSortedSet<K> createKeySet() {
    // the keySet() of the delegate is only a Set and TreeMap.navigatableKeySet

      synchronized (mutex) {
        delegate().clear();
      }
    }

    @Override
    public Set<K> keySet() {
      synchronized (mutex) {
        if (keySet == null) {
          keySet = typePreservingSet(delegate().keySet(), mutex);
        }
        return keySet;
      }
    }

    @Override
    public Collection<V> values() {
      synchronized (mutex) {

    }

    @LazyInit private transient @Nullable Set<K> keySet;

    @Override
    public Set<K> keySet() {
      Set<K> result = keySet;
      return (result == null) ? keySet = createKeySet() : result;
    }

    Set<K> createKeySet() {
      return new KeySet<>(this);
    }

    @LazyInit private transient @Nullable Collection<V> values;