code: def __init__(self, ds1, ds2, windowSize):
      # We're going to use datetime aligned versions of the dataseries.
      self.__ds1, self.__ds2 = aligned.datetime_aligned(ds1, ds2)
      self.__windowSize = windowSize
      self.__hedgeRatio = None
      self.__spread = None
      self.__spreadMean = None
      self.__spreadStd = None
      self.__zScore = None
  
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 1 to create a new StatArbHelper object  with example: obj = StatArbHelper(ds1, ds2, windowSize)