code: def subset(self, *args):
          
          args = list(args)
          args.extend([x for x in
                       self.__grouping.grouping_colnames if x not in args])
          return GroupedDataFrame(self.__grouping.ungroup().subset(*args),
                                  *self.__grouping.grouping_colnames)
docs: Subset only some of the columns of the DataFrame.
  
          :param args: list of column names of the object that should be subsetted
          :type args: tuple
          :return: returns DataFrame with only the columns you selected
          :rtype: DataFrame