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: 20200817101012_add_user_and_lock_stamp.rb
    path of file: ./repos/ekylibre/db/migrate
    
    the code of the file until where you have to start completion: class AddUserAndLockStamp < ActiveRecord::Migration[4.2]
  AFFECTED_TABLES = %i[cvi_cadastral_plants cvi_cadastral_
    
  def self.up
    AFFECTED_TABLES.each do |t|
      add_column t, :lock_version, :integer, null: false, default: 0
      add_reference t, :creator, index: true
      add_reference t, :updater, index: true
    end
  end