} else {
      Map<E, N> incidentEdgeMap =
          Maps.asMap(network.incidentEdges(node), adjacentNodeFn(network, node));
      return network.allowsParallelEdges()
          ? UndirectedMultiNetworkConnections.ofImmutable(incidentEdgeMap)
          : UndirectedNetworkConnections.ofImmutable(incidentEdgeMap);
    }
  }

  private static <N, E> Function<E, N> sourceNodeFn(Network<N, E> network) {