from future import (absolute_import, division, print_function,
unicode_literals)
import backtrader as bt
from ccxtbt import CCXTStore
from datetime import datetime, timedelta

class St(bt.Strategy):
def logdata(self):
txt = []
txt.append('{}'.format(len(self)))

    txt.append('{}'.format(
        self.data.datetime.datetime(0).isoformat())
    )
    txt.append('{:.2f}'.format(self.data.open[0]))
    txt.append('{:.2f}'.format(self.data.high[0]))
    txt.append('{:.2f}'.format(self.data.low[0]))
    txt.append('{:.2f}'.format(self.data.close[0]))
    txt.append('{:.2f}'.format(self.data.volume[0]))
    print(','.join(txt))

def next(self):
    self.logdata()

def main(args=None):
cerebro = bt.Cerebro(quicknotify=True)
config = {'apiKey': '****************',
'secret': '********************',
'enableRateLimit': True,
}

store = CCXTStore(exchange='bitmex', currency='XBT', config=config, retries=5, debug=False, sandbox=True)

broker_mapping = {
    'order_types': {
        bt.Order.Market: 'market',
        bt.Order.Limit: 'limit',
        bt.Order.Stop: 'stop',  # stop-loss for kraken, stop for bitmex
        bt.Order.StopLimit: 'stop limit'
    },
    'mappings': {
        'closed_order': {
            'key': 'status',
            'value': 'closed'
        },
        'canceled_order': {
            'key': 'result',
            'value': 1}
    }
}

broker = store.getbroker(broker_mapping=broker_mapping)
cerebro.setbroker(broker)

hist_start_date = datetime.utcnow() - timedelta(minutes=50)
data = store.getdata(dataname='XBT/BTC', name="XBTBTC",
                     timeframe=bt.TimeFrame.Minutes, fromdate=hist_start_date,
                     compression=1, ohlcv_limit=50, drop_newest=True)


cerebro.resampledata(data, timeframe=bt.TimeFrame.Seconds,
                     compression=10)
cerebro.addstrategy(St)
cerebro.run()
cerebro.plot(style="candlesticks")

if name == 'main':
main()

Got this: if balance == 0 or not balance['free'][currency]
KeyError: 'XBT'

Considering that I am using sandbox account, whats wrong with code?