if (connections.removeSuccessor(node) != null) {
        connections.removePredecessor(node);
        --edgeCount;
      }
    }

    for (N successor : ImmutableList.copyOf(connections.successors())) {
      // requireNonNull is safe because the node is a successor.
      requireNonNull(nodeConnections.getWithoutCaching(successor)).removePredecessor(node);
      requireNonNull(connections.removeSuccessor(successor));

        (N incidentNode) -> EndpointPair.unordered(thisNode, incidentNode));
  }

  @Override
  public @Nullable V value(N node) {
    return adjacentNodeValues.get(node);
  }

  @Override
  public void removePredecessor(N node) {
    @SuppressWarnings("unused")
    V unused = removeSuccessor(node);
  }

  @Override
  public @Nullable V removeSuccessor(N node) {
    return adjacentNodeValues.remove(node);
  }