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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 tx_extend(partial_tx_hex, new_inputs, new_outputs, blockchain='bitcoin', **blockchain_opts):
 """ Add a set of inputs and outputs to a tx. Return the new tx on success Raise on error """

    if blockchain == 'bitcoin':
        return btc_tx_extend(partial_tx_hex, new_inputs, new_outputs, **blockchain_opts)
    else:
        raise ValueError('Unknown blockchain "{}"'.format(blockchain))