code: function (cls) {
          if (cls && !this.contains(cls)) {
            this.cls._map[cls] = true;
            this.cls.push(cls);
            this._change();
          }
  
          return this;
        }
docs: Adds a new class to the class list.
  
  @method add
  @param {String} cls Class to be added.
  @return {tinymce.ui.ClassList} Current class list instance.