code: def _getStartRow(self, bookmark):
      
      bookMarkDict = json.loads(bookmark)
  
      realpath = os.path.realpath(self._filename)
  
      bookMarkFile = bookMarkDict.get('filepath', None)
  
      if bookMarkFile != realpath:
        print ("Ignoring bookmark due to mismatch between File's "
               "filename realpath vs. bookmark; realpath: %r; bookmark: %r") % (
          realpath, bookMarkDict)
        return 0
      else:
        return bookMarkDict['currentRow']
docs: Extracts start row from the bookmark information