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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 encipher(self,string):
 """Encipher string using Foursquare cipher according to initialised key. Punctuation and whitespace are removed from the input. If the input plaintext is not an even number of characters, an 'X' will be appended. Example:: ciphertext = Foursquare(key1='zgptfoihmuwdrcnykeqaxvsbl',key2='mfnbdcrhsaxyogvituewlqzkp').encipher(plaintext) :param string: The string to encipher. :returns: The enciphered string. """
                
        string = self.remove_punctuation(string)  
        if len(string)%2 == 1: string = string + 'X'
        ret = ''
        for c in range(0,len(string.upper()),2):
            a,b = self.encipher_pair(string[c],string[c+1])
            ret += a + b
        return ret