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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 getMessageSignature(self, message):
 """Return the signature of a message. If I am not a sign-all association, the message must have a signed list. @return: the signature, base64 encoded @rtype: str @raises ValueError: If there is no signed list and I am not a sign-all type of association. """

        pairs = self._makePairs(message)
        return oidutil.toBase64(self.sign(pairs))