code: def _batch_gvcfs(data, region, vrn_files, ref_file, out_file=None):
      
      if out_file is None:
          out_file = vrn_files[0]
      # group to get below the maximum batch size, using 200 as the baseline
      max_batch = int(dd.get_joint_group_size(data))
      if len(vrn_files) > max_batch:
          out = []
          num_batches = int(math.ceil(float(len(vrn_files)) / max_batch))
          for i, batch_vrn_files in enumerate(tz.partition_all(num_batches, vrn_files)):
              base, ext = utils.splitext_plus(out_file)
              batch_out_file = "%s-b%s%s" % (base, i, ext)
              out.append(run_combine_gvcfs(batch_vrn_files, region, ref_file, batch_out_file, data))
          return _batch_gvcfs(data, region, out, ref_file)
      else:
          return vrn_files
docs: Perform batching of gVCF files if above recommended input count.