code: def PackageVariable(key, help, default, searchfunc=None):
      # NB: searchfunc is currently undocumented and unsupported
      
      help = '\n    '.join(
          (help, '( yes | no | /path/to/%s )' % key))
      return (key, help, default,
              lambda k, v, e: _validator(k,v,e,searchfunc),
              _converter)
docs: The input parameters describe a 'package list' option, thus they
      are returned with the correct converter and validator appended. The
      result is usable for input to opts.Add() .
  
      A 'package list' option may either be 'all', 'none' or a list of
      package names (separated by space).