/**
   * Creates a graph from a list of node pairs (encoded as strings, e.g. "ab" means that this graph
   * has an edge between 'a' and 'b').
   *
   * <p>The {@code successors} are always returned in alphabetical order.
   */
  private static SuccessorsFunction<Character> createGraph(boolean directed, String... edges) {
    ImmutableMultimap.Builder<Character, Character> graphMapBuilder = ImmutableMultimap.builder();

  /**
   * Creates a graph from a list of node pairs (encoded as strings, e.g. "ab" means that this graph
   * has an edge between 'a' and 'b').
   *
   * <p>The {@code successors} are always returned in alphabetical order.
   */
  private static SuccessorsFunction<Character> createGraph(boolean directed, String... edges) {
    ImmutableMultimap.Builder<Character, Character> graphMapBuilder = ImmutableMultimap.builder();