def decipher(self,string):
return self.encipher(string)<EOL>
Decipher string using Porta cipher according to initialised key. Punctuation and whitespace
        are removed from the input. For the Porta cipher, enciphering and deciphering are the same operation.

        Example::

            plaintext = Porta('HELLO').decipher(ciphertext)     

        :param string: The string to decipher.
        :returns: The deciphered string.