}

    @Override
    public @Nullable K higherKey(@ParametricNullness K key) {
      return sortedMap().higherKey(key);
    }

    @Override
    public @Nullable Entry<K, Collection<V>> firstEntry() {
      Entry<K, Collection<V>> entry = sortedMap().firstEntry();
      return (entry == null) ? null : wrapEntry(entry);
    }

    @Override

    }

    @Override
    public @Nullable K higherKey(@ParametricNullness K key) {
      return sortedMap().higherKey(key);
    }

    @Override
    public @Nullable Entry<K, Collection<V>> firstEntry() {
      Entry<K, Collection<V>> entry = sortedMap().firstEntry();
      return (entry == null) ? null : wrapEntry(entry);
    }

    @Override

        }

        @Override
        public Entry<C, V> next() {
          return wrapEntry(iterator.next());
        }

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

    Entry<C, V> wrapEntry(Entry<C, V> entry) {
      return new ForwardingMapEntry<C, V>() {
        @Override