}

  /**
   * A builder for creating {@link ImmutableValueGraph} instances, especially {@code static final}
   * graphs. Example:
   *
   * <pre>{@code
   * static final ImmutableValueGraph<City, Distance> CITY_ROAD_DISTANCE_GRAPH =
   *     ValueGraphBuilder.undirected()
   *         .<City, Distance>immutable()
   *         .putEdgeValue(PARIS, BERLIN, kilometers(1060))
   *         .putEdgeValue(PARIS, BRUSSELS, kilometers(317))