code: async def _assert_link_secret(self, action: str) -> str:
          
  
          rv = await self.wallet.get_link_secret_label()
          if rv is None:
              LOGGER.debug('HolderProver._assert_link_secret: action %s requires link secret but it is not set', action)
              raise AbsentLinkSecret('Action {} requires link secret but it is not set'.format(action))
  
          return rv
docs: Return current wallet link secret label. Raise AbsentLinkSecret if link secret is not set.
  
          :param action: action requiring link secret