throw new AssertionError(incidentEdgeOrder.type());
    }

    return new DirectedGraphConnections<>(
        /* adjacentNodeValues= */ new HashMap<N, Object>(initialCapacity, INNER_LOAD_FACTOR),
        orderedNodeConnections,
        /* predecessorCount= */ 0,
        /* successorCount= */ 0);
  }

  static <N, V> DirectedGraphConnections<N, V> ofImmutable(

            // requireNonNull is safe because the endpoint pair comes from the graph.
            requireNonNull(graph.edgeValueOrDefault(node, successorNode, null));
    return graph.isDirected()
        ? DirectedGraphConnections.ofImmutable(
            node, graph.incidentEdges(node), successorNodeToValueFn)
        : UndirectedGraphConnections.ofImmutable(
            Maps.asMap(graph.adjacentNodes(node), successorNodeToValueFn));
  }