# the code

  has_many :line_items do
    def total
      require 'pp'
      pp to_a
      if self[0] == self[1]
        self[1..-1].map(&:total).sum
      else
        map(&:total).sum
      end
      # self[1..-1].map(&:total).sum
    end
  end



# result from pp =>
[#<LineItem _id: 4e4d34f7bb71f923eb000001, _type: nil, name: "Hazelfern", image: nil, item_id: "A2750", invent_size_id: "", invent_color_id: "", config_id: "", configure: {}, quantity: 1, price: 295.0, delivery_status: nil, order_id: BSON::ObjectId('4e4d3352bb71f923ae000001')>,
 #<LineItem _id: 4e4d34f7bb71f923eb000001, _type: nil, name: "Hazelfern", image: nil, item_id: "A2750", invent_size_id: "", invent_color_id: "", config_id: "", configure: {}, quantity: 1, price: 295.0, delivery_status: nil, order_id: BSON::ObjectId('4e4d3352bb71f923ae000001')>]