code: def add_input(self, input_):
          
          if not isinstance(input_, Input):
              raise TypeError('`input_` must be a Input instance')
          self.inputs.append(input_)
docs: Adds an input to a Transaction's list of inputs.
  
              Args:
                  input_ (:class:`~bigchaindb.common.transaction.
                      Input`): An Input to be added to the Transaction.