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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 decode_int(self, str):
 """ Decodes a short Base64 string into an integer. Example: ``decode_int('B7')`` returns ``123``. """

        n = 0
        for c in str:
            n = n * self.BASE + self.ALPHABET_REVERSE[c]
        return n