code: function(data, options) {
      if (typeof data.length !== 'undefined') {
        if (typeof data[0].length !== 'undefined') {
          this.grouped = true;
  
          // TODO: Find longest?
          this.group_size = data[0].length;
          var o = {}, k, i = 0;
          for (k in options.labels) {
            k = options.labels[k];
            o[k] = data[i];
            i++;
          }
          return o;
        } else {
          return { 'one': data };
        }
      } else {
        return data;
      }
    }
docs: Overridden to handle grouped bar graphs