def group(self, *args):
args = list(args)<EOL>args.extend([x for x in<EOL>self.__grouping.grouping_colnames if x not in args])<EOL>return GroupedDataFrame(self.__grouping.ungroup(), *args)<EOL>
Group the DataFrame into row-subsets.

:param args: list of column names taht should be used for grouping
:type args: tuple
:return: returns a dataframe that has grouping information
:rtype: GroupedDataFrame