code: def unspent_outputs(self):
          
          if self.operation == Transaction.CREATE:
              self._asset_id = self._id
          elif self.operation == Transaction.TRANSFER:
              self._asset_id = self.asset['id']
          return (UnspentOutput(
              transaction_id=self._id,
              output_index=output_index,
              amount=output.amount,
              asset_id=self._asset_id,
              condition_uri=output.fulfillment.condition_uri,
          ) for output_index, output in enumerate(self.outputs))
docs: UnspentOutput: The outputs of this transaction, in a data
          structure containing relevant information for storing them in
          a UTXO set, and performing validation.