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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 _add_secret_hash(self, parameters, key):
 """ Helper function that computes SecretHash and adds it to a parameters dictionary at a specified key """

        if self.client_secret is not None:
            secret_hash = AWSSRP.get_secret_hash(self.username, self.client_id,
                                                 self.client_secret)
            parameters[key] = secret_hash