code: def _merge_summary(in_files, out_file, data):
      
      if not utils.file_exists(out_file):
          with file_transaction(data, out_file) as tx_out_file:
              with open(tx_out_file, "w") as out_handle:
                  for i, in_file in enumerate(in_files):
                      with open(in_file) as in_handle:
                          for j, line in enumerate(in_handle):
                              if j == 0:
                                  if i == 0:
                                      out_handle.write(line)
                              else:
                                  out_handle.write(line)
      return out_file
docs: Create one big summary file for disambiguation from multiple splits.