transient Supplier<? extends SortedSet<V>> factory;
    transient @Nullable Comparator<? super V> valueComparator;

    CustomSortedSetMultimap(Map<K, Collection<V>> map, Supplier<? extends SortedSet<V>> factory) {
      super(map);
      this.factory = checkNotNull(factory);
      valueComparator = factory.get().comparator();
    }

    @Override
    Set<K> createKeySet() {

        return delegate().replaceValues(key, values); // copy not synchronized
      }
    }

    @Override
    public @Nullable Comparator<? super V> valueComparator() {
      synchronized (mutex) {
        return delegate().valueComparator();
      }
    }

    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;
  }

        return delegate().replaceValues(key, values); // copy not synchronized
      }
    }

    @Override
    public @Nullable Comparator<? super V> valueComparator() {
      synchronized (mutex) {
        return delegate().valueComparator();
      }
    }

    @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;
  }

     */
    @CanIgnoreReturnValue
    @Override
    @Deprecated
    @DoNotCall("Always throws UnsupportedOperationException")
    public final Builder<K, V> orderEntriesByValue(Comparator<? super V> valueComparator) {
      throw new UnsupportedOperationException("Not available on ImmutableSortedMap.Builder");
    }

    /*
     * While the current implementation returns `this`, that's not something we mean to guarantee.