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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 password(self, value=None):
 """ Return or set the password :param string value: the new password to use :returns: string or new :class:`URL` instance """

        if value is not None:
            return URL._mutate(self, password=value)
        return unicode_unquote(self._tuple.password)