Create unsigned rawtx with given txins/txouts as json data.
        <txins>: '[{"txid" : hexdata, "index" : integer}, ...]'
        <txouts>: '[{"address" : hexdata, "value" : satoshis}, ...]'

def create_tx(self, txins=None, txouts=None, lock_time=0):
        """Create unsigned rawtx with given txins/txouts as json data.
        <txins>: '[{"txid" : hexdata, "index" : integer}, ...]'
        <txouts>: '[{"address" : hexdata, "value" : satoshis}, ...]'
        """
        txins = [] if txins is None else txins
        txouts = [] if txouts is None else txouts
        lock_time = deserialize.positive_integer(lock_time)
        txins = deserialize.txins(txins)
        txouts = deserialize.txouts(self.testnet, txouts)
        tx = control.create_tx(self.service, self.testnet, txins, txouts,
                               lock_time=lock_time)
        return serialize.tx(tx)