code: def merge_batch_results(self, result_ids):
          
          outfile = open(self.output().path, 'w')
  
          if self.content_type.lower() == 'csv':
              for i, result_id in enumerate(result_ids):
                  with open("%s.%d" % (self.output().path, i), 'r') as f:
                      header = f.readline()
                      if i == 0:
                          outfile.write(header)
                      for line in f:
                          outfile.write(line)
          else:
              raise Exception("Batch result merging not implemented for %s" % self.content_type)
  
          outfile.close()
docs: Merges the resulting files of a multi-result batch bulk query.