code: def getBookmark(self):
      
  
      if self._write and self._recordCount==0:
        return None
  
      rowDict = dict(filepath=os.path.realpath(self._filename),
                     currentRow=self._recordCount)
      return json.dumps(rowDict)
docs: Gets a bookmark or anchor to the current position.
  
      :returns: an anchor to the current position in the data. Passing this
                anchor to a constructor makes the current position to be the first
                returned record.