code: function(json, md, element) {
          var toinsert = this.create_output_subarea(md, CLASS_NAME, MIME_TYPE);
          this.keyboard_manager.register_events(toinsert);
          render(this, json, toinsert[0]);
          element.append(toinsert);
          return toinsert;
      }
docs: `this` is the output area we are appending to