code: def _getTopByClass(self, assetClass):
      # Find the instrument with the highest rank.
      ret = None
      highestRank = None
      for instrument in self.__instrumentsByClass[assetClass]:
          rank = self._getRank(instrument)
          if rank is not None and (
              highestRank is None or rank > highestRank
          ):
              highestRank = rank
              ret = instrument
      return ret
  
imports: from __future__ import print_function
  from pyalgotrade import strategy
  from pyalgotrade import plotter
  from pyalgotrade.barfeed import yahoofeed
  from pyalgotrade.technical import ma
  from pyalgotrade.technical import cumret
  from pyalgotrade.stratanalyzer import sharpe
  from pyalgotrade.stratanalyzer import returns
label_desc: Use image node_id 4 for calling the MarketTiming obj's underlying member method code with example usage: obj._getTopByClass(assetClass) and returns: ret