code: def buySpread(self, bars, hedgeRatio):
      amount1, amount2 = self.__getOrderSize(bars, hedgeRatio)
      self.marketOrder(self.__i1, amount1)
      self.marketOrder(self.__i2, amount2 * -1)
  
imports: from __future__ import print_function
  from pyalgotrade import strategy
  from pyalgotrade import dataseries
  from pyalgotrade.dataseries import aligned
  from pyalgotrade import plotter
  from pyalgotrade.barfeed import yahoofeed
  from pyalgotrade.stratanalyzer import sharpe
  import numpy
  import statsmodels.api
label_desc: Use image node_id 5 for calling the StatArb obj's underlying member method code with example usage: obj.buySpread(bars, hedgeRatio) without return types