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);
  }

  @Override
  public void addPredecessor(N node, V value) {
    @SuppressWarnings("unused")

    if (connections == null) {
      return false;
    }

    if (allowsSelfLoops()) {
      // Remove self-loop (if any) first, so we don't get CME while removing incident edges.
      if (connections.removeSuccessor(node) != null) {
        connections.removePredecessor(node);
        --edgeCount;
      }
    }

    for (N successor : ImmutableList.copyOf(connections.successors())) {

  /**
   * Remove {@code node} from the set of successors. Returns the value previously associated with
   * the edge connecting the two nodes.
   */
  @CanIgnoreReturnValue
  @Nullable V removeSuccessor(N node);

  /**
   * 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.
   */