code: def main():
      
      parser = argparse.ArgumentParser(
          description='monoseq: pretty-printing DNA and protein sequences',
          epilog='If INPUT is in FASTA format, each record is pretty-printed '
          'after printing its name and ANNOTATION (if supplied) is used by '
          'matching chromosome/record name. If INPUT contains a raw sequence, '
          'only the first chromosome in ANNOTATION is used.')
      parser.add_argument(
          'sequence_file', metavar='INPUT', nargs='?', default=sys.stdin,
          type=argparse.FileType('r'), help='file to read sequence(s) from, '
          'can be in FASTA format (default: standard input)')
      parser.add_argument(
          '-b', '--block-length', metavar='LENGTH', dest='block_length',
          type=int, default=10, help='block length in letters (default: 10)')
      parser.add_argument(
          '-l', '--blocks-per-line', metavar='BLOCKS', dest='blocks_per_line',
          type=int, default=6, help='blocks per line (default: 6)')
      parser.add_argument(
          '-a', '--annotation', metavar='POS', dest='annotation', nargs=2,
          action='append', type=int, help='first and last positions of '
          'subsequence to annotate (allowed more than once)')
      parser.add_argument(
          '-e', '--bed', metavar='ANNOTATION', dest='annotation_file',
          type=argparse.FileType('r'), help='file to read annotation from in '
          'BED format')
  
      args = parser.parse_args()
      pprint(_until_eof(args.sequence_file), annotation=args.annotation,
             annotation_file=args.annotation_file,
             block_length=args.block_length,
             blocks_per_line=args.blocks_per_line)
docs: Command line interface.