code: def peekDateTime(self):
      ret = None
  
      for instrument, bars in six.iteritems(self.__bars):
          nextPos = self.__nextPos[instrument]
          if nextPos < len(bars):
              ret = utils.safe_min(ret, bars[nextPos].getDateTime())
      return ret
  
file_path: pyalgotrade/pyalgotrade/barfeed/membf.py
imports: import six
  from pyalgotrade import barfeed
  from pyalgotrade import bar
  from pyalgotrade import utils
label_desc: Use image node_id 9 for calling the BarFeed obj's underlying member method code with example usage: obj.peekDateTime() and returns: ret