code: function(id, data) {
  			data[this.settings.optgroupValueField] = id;
  			if (id = this.registerOptionGroup(data)) {
  				this.trigger('optgroup_add', id, data);
  			}
  		}
docs: Registers a new optgroup for options
  to be bucketed into.
  
  @param {string} id
  @param {object} data