<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def opt(self, name, help, abbrev=None, type=None, choices=None, metavar=None, nargs=None):
 """Describe an option"""

        kw = dict(help=help, type=type, choices=choices, metavar=metavar,
                  nargs=nargs)
        default = self.argdict[name]
        if default is not NODEFAULT:
            kw['default'] = default
            kw['metavar'] = metavar or str_choices(choices) or str(default)
        abbrev = abbrev or '-' + name[0]
        abbrevs = set(args[0] for args, kw in self.all_arguments)
        longname = '--' + name.replace('_', '-')
        if abbrev == '-h' or abbrev in abbrevs:
            # avoid conflicts with predefined abbreviations
            self._add(name, longname, **kw)
        else:
            self._add(name, abbrev, longname, **kw)