@Override
  public ImmutableSet<K> keySet() {
    if (cachedKeySet != null) {
      return cachedKeySet;
    }
    return cachedKeySet = createKeySet();
  }

  ImmutableSet<K> createKeySet() {
    return new ImmutableMapKeySet<K, V>(this);
  }

  UnmodifiableIterator<K> keyIterator() {
    final UnmodifiableIterator<Entry<K, V>> entryIterator = entrySet().iterator();

    ImmutableSet<K> result = keySet;
    return (result == null) ? keySet = createKeySet() : result;
  }

  /*
   * This could have a good default implementation of `return new ImmutableKeySet<K, V>(this)`, but
   * ProGuard can't figure out how to eliminate that default when RegularImmutableMap overrides it.
   */
  abstract ImmutableSet<K> createKeySet();

  UnmodifiableIterator<K> keyIterator() {

    @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;

    @Override
    public Collection<V> values() {

    @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;

    @Override
    public Collection<V> values() {

   * appear in this multimap.
   */
  @Override
  public ImmutableSet<K> keySet() {
    return map.keySet();
  }

  @Override
  Set<K> createKeySet() {
    throw new AssertionError("unreachable");
  }

  /**
   * Returns an immutable map that associates each key with its corresponding values in the

              }
            }
            return new EntryImpl();
          }
        }
        return endOfData();
      }
    }

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

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

      @Override