code: def combine_calls_parallel(samples, run_parallel):
      
      batch_groups, extras = _group_by_batches(samples, _has_ensemble)
      out = []
      if batch_groups:
          processed = run_parallel("combine_calls", ((b, xs, xs[0]) for b, xs in batch_groups.items()))
          for batch_id, callinfo in processed:
              for data in batch_groups[batch_id]:
                  data["variants"].insert(0, callinfo)
                  out.append([data])
      return out + extras
docs: Combine calls using batched Ensemble approach.