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(

    validateEndpoints(endpoints);
    return removeEdge(endpoints.nodeU(), endpoints.nodeV());
  }

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

    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

            // 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));
  }