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