docs: def get_asset_id(self, tx_id):
          """Return the tx_id of the first transaction.
  
          :param tx_id: Transaction id to start the recursive search.
          :return Transaction id parent.
          """
          tx = self.driver.instance.transactions.retrieve(txid=tx_id)
          assert tx is not None
          return tx['id'] if tx['operation'] == 'CREATE' else tx['asset']['id']