code: def _concat_records(items_by_key, input_order):
      
      all_records = []
      for (k, t) in input_order.items():
          if t == "record":
              all_records.append(k)
      out_items_by_key = utils.deepish_copy(items_by_key)
      out_input_order = utils.deepish_copy(input_order)
      if len(all_records) > 1:
          final_k = all_records[0]
          final_v = items_by_key[final_k]
          for k in all_records[1:]:
              final_v += items_by_key[k]
              del out_items_by_key[k]
              del out_input_order[k]
          out_items_by_key[final_k] = final_v
      return out_items_by_key, out_input_order
docs: Concatenate records into a single key to avoid merging.
  
      Handles heterogeneous records that will then be sorted out in
      the processing fuction.