er_id = cell.output_area._bokeh_server_id;
    // Clean up Bokeh references
    if (id != null && id in Bokeh.index) {
      Bokeh.index[id].model.document.clear();
      delete Bokeh.index[id];
    }

    if (server_id !== undefined) {
      // Clean up Bokeh references
      var cmd = "from bokeh.io.state import curstate; print(curstate().uuid_to_server['" + server_id + "'].get_sessions()[0].document.roots[0]._id)";
      cell.notebook.kernel.execute(cmd, {
        iopub: {
          output: function(msg)