docs: public static ValidatorConfiguration createExperimental() {
          Map<Check, Level> checks = getStandardChecks();
  
          checks.put(GdlArityCheck.INSTANCE, Level.ERROR);
          checks.put(GdlNotInRuleHeadCheck.INSTANCE, Level.ERROR);
          checks.put(UnrecognizedGdlArgumentCheck.INSTANCE, Level.WARNING);
  
          // (gdl random)
          checks.put(GdlRandomGoalCheck.INSTANCE, Level.ERROR);
  
          return new ValidatorConfiguration(checks);
      }