@CheckForNull final WrappedCollection ancestor;
    @CheckForNull final Collection<V> ancestorDelegate;

    WrappedCollection(
        @ParametricNullness K key,
        Collection<V> delegate,
        @CheckForNull WrappedCollection ancestor) {
      this.key = key;
      this.delegate = delegate;
      this.ancestor = ancestor;
      this.ancestorDelegate = (ancestor == null) ? null : ancestor.getDelegate();
    }

    @CheckForNull final WrappedCollection ancestor;
    @CheckForNull final Collection<V> ancestorDelegate;

    WrappedCollection(
        @ParametricNullness K key,
        Collection<V> delegate,
        @CheckForNull WrappedCollection ancestor) {
      this.key = key;
      this.delegate = delegate;
      this.ancestor = ancestor;
      this.ancestorDelegate = (ancestor == null) ? null : ancestor.getDelegate();
    }