You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: 20180512013847_makes_barcode_item_polymorphic.rb
    path of file: ./repos/human-essentials/db/migrate
    
    the code of the file until where you have to start completion: # Barcode items need to be able to be attached to either BaseItems or regular Items
class MakesBarcodeItemPolymorphic < ActiveRecord::Migration[5.1]
  def up
    
  def down
  	remove_index :barcode_items, column: [:barcodeable_type, :barcodeable_id]
  	change_table :barcode_items do |t|
  		t.remove :barcodeable_type
  		t.rename :barcodeable_id, :item_id
  	end

  end