code: def _update_header(orig_vcf, base_file, new_lines, chrom_process_fn=None):
      
      new_header = "%s-sample_header.txt" % utils.splitext_plus(base_file)[0]
      with open(new_header, "w") as out_handle:
          chrom_line = None
          with utils.open_gzipsafe(orig_vcf) as in_handle:
              for line in in_handle:
                  if line.startswith("##"):
                      out_handle.write(line)
                  else:
                      chrom_line = line
                      break
          assert chrom_line is not None
          for line in new_lines:
              out_handle.write(line + "\n")
          if chrom_process_fn:
              chrom_line = chrom_process_fn(chrom_line)
          out_handle.write(chrom_line)
      return new_header
docs: Fix header with additional lines and remapping of generic sample names.