code: def add_output(self, output):
          
          if not isinstance(output, Output):
              raise TypeError('`output` must be an Output instance or None')
          self.outputs.append(output)
docs: Adds an output to a Transaction's list of outputs.
  
              Args:
                  output (:class:`~bigchaindb.common.transaction.
                      Output`): An Output to be added to the
                      Transaction.