code: def _write_unassigned_ranges(out_filename):
      
      with open(out_filename, 'wt') as f:
          f.write('# auto-generated by port_for._download_ranges (%s)\n' % datetime.date.today())
          f.write('UNASSIGNED_RANGES = [\n')
          for range in to_ranges(sorted(list(_unassigned_ports()))):
              f.write("    (%d, %d),\n" % range)
          f.write(']\n')
docs: Downloads ports data from IANA & Wikipedia and converts
      it to a python module. This function is used to generate _ranges.py.