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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 tseitin(self, auxvarname='aux'):
 """Convert the expression to Tseitin's encoding."""

        if self.is_cnf():
            return self

        _, constraints = _tseitin(self.to_nnf(), auxvarname)
        fst = constraints[-1][1]
        rst = [Equal(v, ex).to_cnf() for v, ex in constraints[:-1]]
        return And(fst, *rst)