public static String toggleTraceRules() {
    if ((Stella.$TRACED_KEYWORDS$ != null) &&
        Stella.$TRACED_KEYWORDS$.memberP(Logic.KWD_PROPAGATE)) {
      {
        Stella.dropTrace(Cons.cons(Logic.KWD_PROPAGATE, Stella.NIL));
        return ("Rule tracing disabled.");
      }
    }
    else {
      {
        Stella.addTrace(Cons.cons(Logic.KWD_PROPAGATE, Stella.NIL));
        return ("Rule tracing enabled.");
      }
    }
  }