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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_did_providers(self, did):
 """ Return the list providers registered on-chain for the given did. :param did: hex str the id of an asset on-chain :return: list of addresses None if asset has no registerd providers """

        register_values = self.contract_concise.getDIDRegister(did)
        if register_values and len(register_values) == 5:
            return DIDRegisterValues(*register_values).providers

        return None