           Modifies original list by adding all the elements from another list.
            
            @param items: List of elements to add.
            @return Returns <code>true</code> if the list was changed as a result of the call; otherwise <code>false</code>.
        */
        public function addItems(items:IList):Boolean {
            this._collection = this._collection.concat(items.toArray());
            
            return true;
        }
        
        /**
            Modifies original list