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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 finalize(self):
 """Finalizes the signer and returns the signature. :returns: Calculated signer signature :rtype: bytes """

        prehashed_digest = self._hasher.finalize()
        return _ecc_static_length_signature(key=self.key, algorithm=self.algorithm, digest=prehashed_digest)