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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 string_to_sign(self):
 """ The AWS SigV4 string being signed. """

        return (AWS4_HMAC_SHA256 + "\n" +
                self.request_timestamp + "\n" +
                self.credential_scope + "\n" +
                sha256(self.canonical_request.encode("utf-8")).hexdigest())