code: function(new_data, original_data) {
          var key;
          for (key in new_data) {
              if (new_data[key].constructor === Object) {
                  original_data[key] = this._recursive_extend(
                      new_data[key],
                      original_data[key]
                  );
              } else {
                  original_data[key] = new_data[key];
              }
          }
          return original_data;
      }
docs: Recursively puts `new_data` into `original_data`.