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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_input(self, input_):
 """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. """

        if not isinstance(input_, Input):
            raise TypeError('`input_` must be a Input instance')
        self.inputs.append(input_)