on('clear_output.CodeCell', handleClearOutput);
    events.on('delete.Cell', handleClearOutput);

    /* Handle when a new output is added */
    events.on('output_added.OutputArea', handleAddOutput);

    /**
     * Register the mime type and append_mime function with output_area
     */
    OutputArea.prototype.register_mime_type(EXEC_MIME_TYPE, append_mime, {
      /* Is output safe? */
      safe: true,
      /* Index of renderer in `output_area.display_order` */
      index: 0
    });
  }

  // registe