code: def decipher(self,string):
                   
          string = self.remove_punctuation(string)#,filter='[^'+self.chars+']')
          ret = ''
          for i in range(0,len(string),2):
              ret += self.decipher_pair(string[i:i+2])
          return ret
docs: Decipher string using Polybius square cipher according to initialised key.
  
          Example::
  
              plaintext = Polybius('APCZWRLFBDKOTYUQGENHXMIVS',5,'MKSBU').decipher(ciphertext)     
  
          :param string: The string to decipher.
          :returns: The deciphered string. The plaintext will be half the length of the ciphertext.