checkArgument(incidentEdge.nodeU().equals(thisNode));

        N successor = incidentEdge.nodeV();
        V value = successorNodeToValueFn.apply(successor);

        Object existingValue = adjacentNodeValues.put(successor, value);
        if (existingValue != null) {
          checkArgument(existingValue == PRED);
          adjacentNodeValues.put(successor, new PredAndSucc(value));
        }

   */
  private transient int @Nullable [] predecessor;

  /**
   * Pointer to the successor of an entry in insertion order. ENDPOINT indicates a node is the last
   * node in insertion order; all values at indices ≥ {@link #size()} are UNSET.
   */
  private transient int @Nullable [] successor;

  /** Pointer to the first node in the linked list, or {@code ENDPOINT} if there are no entries. */

   */
  private transient int @Nullable [] predecessor;

  /**
   * Pointer to the successor of an entry in insertion order. ENDPOINT indicates a node is the last
   * node in insertion order; all values at indices ≥ {@link #size()} are UNSET.
   */
  private transient int @Nullable [] successor;

  /** Pointer to the first node in the linked list, or {@code ENDPOINT} if there are no entries. */

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it
   * also becomes a successor. Associates {@code value} with the edge connecting the two nodes.
   */
  void addPredecessor(N node, V value);

  /**
   * Add {@code node} as a successor to the origin node. In the case of an undirected graph, it also

                    Iterators.transform(
                        graph.successors(node).iterator(),
                        (N successor) ->
                            graph.isDirected()
                                ? EndpointPair.ordered(node, successor)
                                : EndpointPair.unordered(node, successor)));
              }
            };
        return nodeInvalidatableSet(incident, node);
      }

    }
  }

  private static <T extends @Nullable Object> void successor(AvlNode<T> a, AvlNode<T> b) {
    a.succ = b;
    b.pred = a;
  }

  private static <T extends @Nullable Object> void successor(
      AvlNode<T> a, AvlNode<T> b, AvlNode<T> c) {
    successor(a, b);
    successor(b, c);
  }

  /*

  @CanIgnoreReturnValue
  N removeOutEdge(E edge);

  /**
   * Add {@code edge} to the set of incoming edges. Implicitly adds {@code node} as a predecessor.
   */
  void addInEdge(E edge, N node, boolean isSelfLoop);

  /** Add {@code edge} to the set of outgoing edges. Implicitly adds {@code node} as a successor. */
  void addOutEdge(E edge, N node);

      }

      for (N successor : sanityCheckSet(graph.successors(node))) {
        allEndpointPairs.add(EndpointPair.of(graph, node, successor));
        assertThat(graph.predecessors(successor)).contains(node);
        assertThat(graph.hasEdgeConnecting(node, successor)).isTrue();
        assertThat(graph.incidentEdges(node)).contains(EndpointPair.of(graph, node, successor));
      }

    }
  }

  private static <T extends @Nullable Object> void successor(AvlNode<T> a, AvlNode<T> b) {
    a.succ = b;
    b.pred = a;
  }

  private static <T extends @Nullable Object> void successor(
      AvlNode<T> a, AvlNode<T> b, AvlNode<T> c) {
    successor(a, b);
    successor(b, c);
  }

  /*

      }

      for (N successor : sanityCheckSet(graph.successors(node))) {
        allEndpointPairs.add(EndpointPair.of(graph, node, successor));
        assertThat(graph.predecessors(successor)).contains(node);
        assertThat(graph.hasEdgeConnecting(node, successor)).isTrue();
        assertThat(graph.incidentEdges(node)).contains(EndpointPair.of(graph, node, successor));
      }