code: @Override
      public boolean configure(FeatureContext context) {
          Configuration cfg = context.getConfiguration();
          if (!cfg.isRegistered(CommonExprTransformer.class))
              context.register(CommonExprTransformer.class);
          if (!cfg.isRegistered(CommonExprArgTransformer.class))
              context.register(CommonExprArgTransformer.class);
          if (!cfg.isRegistered(QuerySyntaxExceptionMapper.class))
              context.register(QuerySyntaxExceptionMapper.class);
          return true;
      }
docs: {@inheritDoc}