code: function() {
          if (!this.el) {
              var tagName = joint.util.result(this, 'tagName');
              var attrs = joint.util.assign({}, joint.util.result(this, 'attributes'));
              if (this.id) attrs.id = joint.util.result(this, 'id');
              this.setElement(this._createElement(tagName));
              this._setAttributes(attrs);
          } else {
              this.setElement(joint.util.result(this, 'el'));
          }
          this._ensureElClassName();
      }
docs: Override the Backbone `_ensureElement()` method in order to create an svg element (e.g., `<g>`) node that wraps all the nodes of the Cell view. Expose class name setter as a separate method.