|2lt5/qFtgUpEon2j06rd/0+ODqqVJX+6d3SpmF1fPfKUB6AOZbxEkaJpBSTavoTg
      |G2M/NMdjZjrcB3quNQcLg54mmI3HJm1zOd/8i2fZjvoiyVY30Inn2SmQsAotXw1u
      |aE/319bnR2sQlnkp6MJU0eLEtKyRif/IODvY+mtRYYdkFtoeT6qQPMIh+gF/H3to
      |5tjs3g59QC8k2TJDop4EFYUOwdrtnb8wUiBnLyURD1szASE2IO2Ftk1zaNOPKtrv
      |VeJuB/mpAgMBAAGjIDAeMBwGA1UdEQEB/wQSMBCHBAEBAQGCCGNhc2guYXBwMA0G
      |CSqGSIb3DQEBCwUAA4IBAQAPm7vfk+rxSucxxbFiimmFKBw+ymieLY/kznNh0lHJ

   *    d   e   g
   *   /|\      |
   *  / | \     |
   * a  b  c    f
   * }
   */
  private static final SuccessorsFunction<Character> TREE =
      createDirectedGraph("hd", "he", "hg", "da", "db", "dc", "gf");

  /**
   * Two disjoint tree-shaped graphs that look as follows (all edges are directed facing downwards):
   *
   * {@snippet :
   * a   c
   * |   |
   * |   |
   * b   d
   * }
   */

   *    d   e   g
   *   /|\      |
   *  / | \     |
   * a  b  c    f
   * }
   */
  private static final SuccessorsFunction<Character> TREE =
      createDirectedGraph("hd", "he", "hg", "da", "db", "dc", "gf");

  /**
   * Two disjoint tree-shaped graphs that look as follows (all edges are directed facing downwards):
   *
   * {@snippet :
   * a   c
   * |   |
   * |   |
   * b   d
   * }
   */