code: def encipher(self,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
docs: 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.