code: def aggregateByKey(self, zeroValue, seqFunc, combFunc, numPartitions=None,
                         partitionFunc=portable_hash):
          
          def createZero():
              return copy.deepcopy(zeroValue)
  
          return self.combineByKey(
              lambda v: seqFunc(createZero(), v), seqFunc, combFunc, numPartitions, partitionFunc)
docs: Aggregate the values of each key, using given combine functions and a neutral
          "zero value". This function can return a different result type, U, than the type
          of the values in this RDD, V. Thus, we need one operation for merging a V into
          a U and one operation for merging two U's, The former operation is used for merging
          values within a partition, and the latter is used for merging values between
          partitions. To avoid memory allocation, both of these functions are
          allowed to modify and return their first argument instead of creating a new U.