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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 dummy_signatures(self):
 """Create a dummy signature. This is used when initially writing the MAR header and we don't know what the final signature data will be. Returns: Fake signature data suitable for writing to the header with .write_signatures() """

        if not self.signing_algorithm:
            return []
        algo_id = {'sha1': 1, 'sha384': 2}[self.signing_algorithm]
        signature = make_dummy_signature(algo_id)
        return [(algo_id, signature)]