code: def _register_attribute(self, did, checksum, value, account, providers):
          
          assert isinstance(providers, list), ''
          return self.send_transaction(
              'registerAttribute',
              (did,
               checksum,
               providers,
               value),
              transact={'from': account.address,
                        'passphrase': account.password}
          )
docs: Register an DID attribute as an event on the block chain.
  
          :param did: 32 byte string/hex of the DID
          :param checksum: checksum of the ddo, hex str
          :param value: url for resolve the did, str
          :param account: account owner of this DID registration record
          :param providers: list of providers addresses