code: def decode(self, ciphertext):
          "Search for a decoding of the ciphertext."
          self.ciphertext = ciphertext
          problem = PermutationDecoderProblem(decoder=self)
          return search.best_first_tree_search(
              problem, lambda node: self.score(node.state)f decode(self, ciphertext):
          "Search for a decoding of the ciphertext."
          self.ciphertext = ciphertext
          problem = PermutationDecoderProblem(decoder=self)
          return search.best_first_tree_search(
              problem, lambda node: self.score(node.state))
docs: Search for a decoding of the ciphertext.