docs: @Override
    public <T> Streamlet<T> applyOperator(IStreamletOperator<R, T> operator) {
      checkNotNull(operator, "operator cannot be null");
  
      // By default, NoneStreamGrouping stategy is used. In this stategy, tuples are forwarded
      // from parent component to a ramdon one of all the instances of the child component,
      // which is the same logic as shuffle grouping.
      return applyOperator(operator, new NoneStreamGrouping());
    }