}

  static <N, E> UndirectedNetworkConnections<N, E> of() {
    return new UndirectedNetworkConnections<>(HashBiMap.<E, N>create(EXPECTED_DEGREE));
  }

  static <N, E> UndirectedNetworkConnections<N, E> ofImmutable(Map<E, N> incidentEdges) {
    return new UndirectedNetworkConnections<>(ImmutableBiMap.copyOf(incidentEdges));
  }

  @Override
  public Set<N> adjacentNodes() {

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

  /**

            new LinkedHashMap<N, V>(INNER_CAPACITY, INNER_LOAD_FACTOR));
      default:
        throw new AssertionError(incidentEdgeOrder.type());
    }
  }

  static <N, V> UndirectedGraphConnections<N, V> ofImmutable(Map<N, V> adjacentNodeValues) {
    return new UndirectedGraphConnections<>(ImmutableMap.copyOf(adjacentNodeValues));
  }

  @Override
  public Set<N> adjacentNodes() {

    Function<N, Presence> edgeValueFn =
        (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;
  }

  /**

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

  /**

            new LinkedHashMap<N, V>(INNER_CAPACITY, INNER_LOAD_FACTOR));
      default:
        throw new AssertionError(incidentEdgeOrder.type());
    }
  }

  static <N, V> UndirectedGraphConnections<N, V> ofImmutable(Map<N, V> adjacentNodeValues) {
    return new UndirectedGraphConnections<>(ImmutableMap.copyOf(adjacentNodeValues));
  }

  @Override
  public Set<N> adjacentNodes() {

    return new UndirectedMultiNetworkConnections<>(
        new HashMap<E, N>(INNER_CAPACITY, INNER_LOAD_FACTOR));
  }

  static <N, E> UndirectedMultiNetworkConnections<N, E> ofImmutable(Map<E, N> incidentEdges) {
    return new UndirectedMultiNetworkConnections<>(ImmutableMap.copyOf(incidentEdges));
  }

  @CheckForNull @LazyInit private transient Reference<Multiset<N>> adjacentNodesReference;

        orderedNodeConnections,
        /* predecessorCount = */ 0,
        /* successorCount = */ 0);
  }

  static <N, V> DirectedGraphConnections<N, V> ofImmutable(
      N thisNode, Iterable<EndpointPair<N>> incidentEdges, Function<N, V> successorNodeToValueFn) {
    checkNotNull(thisNode);
    checkNotNull(successorNodeToValueFn);