code: def __init__(self, feed, brk):
      super(Strategy, self).__init__(feed, brk)
      smaPeriod = 20
      self.__instrument = "BTC"
      self.__prices = feed[self.__instrument].getCloseDataSeries()
      self.__sma = ma.SMA(self.__prices, smaPeriod)
      self.__bid = None
      self.__ask = None
      self.__position = None
      self.__posSize = 0.05
  
      # Subscribe to order book update events to get bid/ask prices to trade.
      feed.getOrderBookUpdateEvent().subscribe(self.__onOrderBookUpdate)
  
file_path: pyalgotrade/samples/tutorial_bitstamp_1.py
imports: from pyalgotrade.bitstamp import barfeed
  from pyalgotrade.bitstamp import broker
  from pyalgotrade import strategy
  from pyalgotrade.technical import ma
  from pyalgotrade.technical import cross
label_desc: Use image node_id 1 to create a new Strategy object from inherited base classes: strategy with example: obj = Strategy(feed, brk)