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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def arg(self, name, help, type=None, choices=None, metavar=None, nargs=None):
 """Describe a positional argument"""

        kw = dict(help=help, type=type, choices=choices, metavar=metavar,
                  nargs=nargs)
        default = self.argdict[name]
        if default is not NODEFAULT:
            kw['nargs'] = nargs or '?'
            kw['default'] = default
            kw['help'] = kw['help'] + ' [default: %s]' % repr(default)
        self._add(name, name, **kw)