code: public void format(StringBuffer fmt, Set done, Set todo, int indent) {
      formatName(fmt, indent);
      fmt.append("{\n");
      for (int i = 0; i < cases.length; i++) {
        if (i > 0)
          fmt.append(" |\n");
        cases[i].format(fmt, done, todo, indent + 2);
      }
      fmt.append("\n");
      indent(fmt, indent);
      fmt.append("}");
    }
docs: Format for human consumption (subroutine of toString)