code: function register_renderer(notebook, trial, history, utils, d3_selection) {
    /* Get an instance of output_area from a CodeCell instance */
    var _notebook$get_cells$r = notebook.get_cells().reduce(function (result, cell) {
      return cell.output_area ? cell : result;
    }, {}),
        output_area = _notebook$get_cells$r.output_area;
  
    /* History mime */
  
  
    var append_history = function append_history(data, metadata, element) {
      var div = document.createElement('div');
      element.append(div);
      var graph = new history.HistoryGraph('history-' + utils.makeid(), div, {
        width: data.width,
        height: data.height,
        hintMessage: ""
      });
      graph.load(data);
      return div;
    };
  
    /* Trial mime */
    var append_trial = function append_trial(data, metadata, element) {
      var div = document.createElement('div');
      element.append(div);
      var graph = new trial.TrialGraph('trial-' + utils.makeid(), div, {
        width: data.width,
        height: data.height
      });
      graph.load(data, data.trial1, data.trial2);
      return div;
    };
  
    /**
     * Register the mime type and append_history function with output_area
     */
    output_area.register_mime_type('application/noworkflow.history+json', append_history, {
      safe: true,
      index: 0
    });
  
    output_area.register_mime_type('application/noworkflow.trial+json', append_trial, {
      safe: true,
      index: 0
    });
  }
docs: Register the mime type and append_mime function with the notebook's
  output area