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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 download(self):
 """ Downloads the signature. Returns: """

        if not self.can_update():
            self._tcex.handle_error(910, [self.type])

        return self.tc_requests.download(self.api_type, self.api_sub_type, self.unique_id)