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: 20190604110233_fix_phone_configuration_index.rb
    path of file: ./repos/identity-idp/db/primary_migrate
    
    the code of the file until where you have to start completion: class FixPhoneConfigurationIndex < ActiveRecord::Migration[5.1]
  disable_ddl_transaction!
    
  def down
    remove_index :phone_configurations, %i[user_id made_default_at created_at]
    add_index(
      :phone_configurations,
      %i[made_default_at created_at],
      algorithm: :concurrently,
    )
  end