code: def _expand_rec_to_vars(var_items, rec_items, input_order, items_by_key, parallel):
      
      num_items = var_items
      var_items = list(var_items)[0]
      if rec_items:
          for rec_key in (k for (k, t) in input_order.items() if t == "record"):
              rec_vals = items_by_key[rec_key]
              if len(rec_vals) == 1 and var_items > 1:
                  items_by_key[rec_key] = rec_vals * var_items
              else:
                  assert var_items == len(rec_vals), (var_items, rec_vals)
      return items_by_key, num_items
docs: Expand record to apply to number of variants.
  
      Alternative approach to _nest_vars_in_rec
      to combining a single record with multiple variants.