code: def square_off(samples, run_parallel):
      
      to_process = []
      extras = []
      for data in [utils.to_single_data(x) for x in samples]:
          added = False
          if tz.get_in(("metadata", "batch"), data):
              for add in genotype.handle_multiple_callers(data, "jointcaller", require_bam=False):
                  if _is_jointcaller_compatible(add):
                      added = True
                      to_process.append([add])
          if not added:
              extras.append([data])
      processed = grouped_parallel_split_combine(to_process, _split_by_callable_region,
                                                 multi.group_batches_joint, run_parallel,
                                                 "square_batch_region", "concat_variant_files",
                                                 "vrn_file", ["region", "sam_ref", "config"])
      return _combine_to_jointcaller(processed) + extras
docs: Perform joint calling at all variants within a batch.