code: function(attr) {
          var html = this._escapedAttributes[attr];
          if (html) {
            return html;
          }
          var val = this.attributes[attr];
          var escaped;
          if (isNullOrUndefined(val)) {
            escaped = '';
          } else {
            escaped = _.escape(val.toString());
          }
          this._escapedAttributes[attr] = escaped;
          return escaped;
        }
docs: Gets the HTML-escaped value of an attribute.