<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def apply(self, func, *args, **kwargs):
 """Apply the provided function and combine the results together in the same way as apply from groupby in pandas. This returns a DataFrame. """

        self._prep_pandas_groupby()

        def key_by_index(data):
            """Key each row by its index.
            """
            # TODO: Is there a better way to do this?
            for key, row in data.iterrows():
                yield (key, pd.DataFrame.from_dict(
                    dict([(key, row)]), orient='index'))

        myargs = self._myargs
        mykwargs = self._mykwargs
        regroupedRDD = self._distributedRDD.mapValues(
            lambda data: data.groupby(*myargs, **mykwargs))
        appliedRDD = regroupedRDD.map(
            lambda key_data: key_data[1].apply(func, *args, **kwargs))
        reKeyedRDD = appliedRDD.flatMap(key_by_index)
        dataframe = self._sortIfNeeded(reKeyedRDD).values()
        return DataFrame.fromDataFrameRDD(dataframe, self.sql_ctx)