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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 get_response_signer(self):
 """Returns the response signer for this version of the signature. """

        if not hasattr(self, "response_signer"):
            self.response_signer = V2ResponseSigner(self.digest, orig=self)
        return self.response_signer