*/
@ElementTypesAreNonnullByDefault
final class UndirectedGraphConnections<N, V> implements GraphConnections<N, V> {
  private final Map<N, V> adjacentNodeValues;

  private UndirectedGraphConnections(Map<N, V> adjacentNodeValues) {
    this.adjacentNodeValues = checkNotNull(adjacentNodeValues);
  }

  static <N, V> UndirectedGraphConnections<N, V> of(ElementOrder<N> incidentEdgeOrder) {

        (Function<N, Presence>) Functions.constant(Presence.EDGE_EXISTS);
    return graph.isDirected()
        ? DirectedGraphConnections.ofImmutable(node, graph.incidentEdges(node), edgeValueFn)
        : UndirectedGraphConnections.ofImmutable(
            Maps.asMap(graph.adjacentNodes(node), edgeValueFn));
  }

  @Override
  BaseGraph<N> delegate() {
    return backingGraph;
  }

  /**

  }

  private GraphConnections<N, V> newConnections() {
    return isDirected()
        ? DirectedGraphConnections.<N, V>of(incidentEdgeOrder)
        : UndirectedGraphConnections.<N, V>of(incidentEdgeOrder);
  }

    return graph.isDirected()
        ? DirectedGraphConnections.ofImmutable(
            node, graph.incidentEdges(node), successorNodeToValueFn)
        : UndirectedGraphConnections.ofImmutable(
            Maps.asMap(graph.adjacentNodes(node), successorNodeToValueFn));
  }

  /**
   * A builder for creating {@link ImmutableValueGraph} instances, especially {@code static final}