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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_hash(self):
 """ Get the HMAC-SHA1 that has been calculated this far. """

        if not self.executed:
            raise pyhsm.exception.YHSM_Error("HMAC-SHA1 hash not available, before execute().")
        return self.result.hash_result