code: def decipher(self,string,keep_punct=False):
                  
          if not keep_punct: string = self.remove_punctuation(string)    
          ind = range(len(string))
          pos = self.buildfence(ind, self.key)
          return ''.join(string[pos.index(i)] for i in ind)
docs: Decipher string using Railfence cipher according to initialised key.
  
          Example::
          
              plaintext = Railfence(3).decipher(ciphertext)     
  
          :param string: The string to decipher.
          :param keep_punct: if true, punctuation and spacing are retained. If false, it is all removed. Default is False. 
          :returns: The deciphered string.