code: function(data) {
  			var key = hash_key(data[this.settings.optgroupValueField]);
  			if (!key) return false;
  	
  			data.$order = data.$order || ++this.order;
  			this.optgroups[key] = data;
  			return key;
  		}
docs: Registers an option group to the pool of option groups.
  
  @param {object} data
  @return {boolean|string}