code: def main(args=None):
      
      if args is None:
          # parse command-line arguments
          parser = get_argument_parser()
          args = parser.parse_args()
  
      experiment_file = args.experiment_file
      output_file = args.output_file
  
      # log_file = args.log_file
      # quiet = args.quiet
      # verbose = args.verbose
  
      # logger = misc.get_logger(log_file=log_file, quiet=quiet,
      #                          verbose=verbose)
  
      host = 'ftp-trace.ncbi.nlm.nih.gov'
      user = 'anonymous'
      password = 'anonymous'
  
      # output_dir = download_dir + experiment_id + '/'
      # make sure output directory exists
      # misc.make_sure_dir_exists(output_dir)
      # logger.info('Created output directory: "%s".', output_dir)
  
      experiments = misc.read_single(experiment_file)
  
      runs = []
      with ftputil.FTPHost(host, user, password) as ftp_host:
          for exp in experiments:
              exp_dir = '/sra/sra-instant/reads/ByExp/sra/SRX/%s/%s/' \
                      % (exp[:6], exp)
              ftp_host.chdir(exp_dir)
              run_folders = ftp_host.listdir(ftp_host.curdir)
              # logging.info('Found %d run folders.',len(run_folders))
  
              for folder in run_folders:
                  files = ftp_host.listdir(folder)
                  assert len(files) == 1
                  runs.append((exp, folder))
  
      with open(output_file, 'wb') as ofh:
          writer = csv.writer(ofh, dialect='excel-tab',
                              lineterminator=os.linesep,
                              quoting=csv.QUOTE_NONE)
          for r in runs:
              writer.writerow(r)
          
      return 0
docs: Download all .sra from NCBI SRA for a given experiment ID.
  
      Parameters
      ----------
      args: argparse.Namespace object, optional
          The argument values. If not specified, the values will be obtained by
          parsing the command line arguments using the `argparse` module.
  
      Returns
      -------
      int
          Exit code (0 if no error occurred).