code: def _to_reader_frame(self):
      
  
      reader_frame = 'KindleReaderIFrame'
      frame_loaded = lambda br: br.find_elements_by_id(reader_frame)
      self._wait().until(frame_loaded)
  
      self.switch_to.frame(reader_frame)  # pylint: disable=no-member
  
      reader_loaded = lambda br: br.find_elements_by_id('kindleReader_header')
      self._wait().until(reader_loaded)
docs: Navigate to the KindleReader iframe.