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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 _validate(self):
 """ Verify that the stored rank method is valid. """

        if self._method not in _RANK_METHODS:
            raise UnknownRankMethod(
                method=self._method,
                choices=set(_RANK_METHODS),
            )
        return super(Rank, self)._validate()