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: 20190526151359_mod_columns_to_upcoming_event.rb
    path of file: ./repos/coderdojo.jp/db/migrate
    
    the code of the file until where you have to start completion: class ModColumnsToUpcomingEvent < ActiveRecord::Migration[5.1]
  def up
    remove_index :upcoming_events, :event_at

    add_column :upcoming_eve
    
  def down
    remove_index :upcoming_events, [:service_name, :event_id]

    remove_column :upcoming_events, :service_name, :string, null: false
    remove_column :upcoming_events, :participants, :integer, null: false

    add_index :upcoming_events, :event_at, name: "index_upcoming_events_on_event_at"
  end