def add(*items)
        notify_will_change! if items.count > 0
        items.each do |item|
          collection.push item
        end
        @collection
      end
def add(*items)
        notify_will_change! if items.count > 0
        items.each do |item|
          collection.push item
        end
        @collection
      end
Add items to the collection
 @param items [Array] items to add