code: def stats(self, columns):
          
          def reduce_func(sc1, sc2):
              return sc1.merge_pstats(sc2)
  
          return self._rdd.mapPartitions(lambda partition: [
              PStatCounter(dataframes=partition, columns=columns)])\
              .reduce(reduce_func)
docs: Compute the stats for each column provided in columns.
          Parameters
          ----------
          columns : list of str, contains all columns to compute stats on.