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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def decipher(self,string):
 """Decipher string using ADFGVX cipher according to initialised key information. Punctuation and whitespace are removed from the input. Example:: plaintext = ADFGVX('ph0qg64mea1yl2nofdxkr3cvs5zw7bj9uti8','HELLO').decipher(ciphertext) :param string: The string to decipher. :returns: The enciphered string. """
                
        step2 = ColTrans(self.keyword).decipher(string)
        step1 = PolybiusSquare(self.key,size=6,chars='ADFGVX').decipher(step2)
        return step1