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

  /**

    graph.putEdgeValue(2, 1, "2-1");
    graph.putEdgeValue(2, 3, "2-3");
    graph.putEdgeValue(1, 2, "1-2");

    assertThat(graph.incidentEdges(2))
        .containsExactly(
            EndpointPair.ordered(2, 1), EndpointPair.ordered(2, 3), EndpointPair.ordered(1, 2))
        .inOrder();
  }

  @Test

    }

    // Since views are returned, we need to copy the edges that will be removed.
    // Thus we avoid modifying the underlying view while iterating over it.
    for (E edge : ImmutableList.copyOf(connections.incidentEdges())) {
      removeEdge(edge);
    }
    nodeConnections.remove(node);
    return true;
  }

  @Override
  @CanIgnoreReturnValue
  public boolean removeEdge(E edge) {

    graph.putEdgeValue(2, 1, "2-1");
    graph.putEdgeValue(2, 3, "2-3");
    graph.putEdgeValue(1, 2, "1-2");

    assertThat(graph.incidentEdges(2))
        .containsExactly(
            EndpointPair.ordered(2, 1), EndpointPair.ordered(2, 3), EndpointPair.ordered(1, 2))
        .inOrder();
  }

  @Test

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

  /**