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: 117_create_signed_up_users.rb
    path of file: ./repos/expertiza/db/migrate
    
    the code of the file until where you have to start completion: class CreateSignedUpUsers < ActiveRecord::Migration[4.2]
  def self.up
    create_table :signed_up_user
    
  def self.up
    create_table :signed_up_users do |t|
      t.column :topic_id, :integer, null: false
      t.column :creator_id, :integer, null: false
      t.column :is_waitlisted, :boolean, null: false
      t.column :preference_priority_number, :integer
    end

    add_index 'signed_up_users', ['topic_id'], name: 'fk_signed_up_users_sign_up_topics'

    execute "alter table signed_up_users
             add constraint fk_signed_up_users_sign_up_topics
             foreign key (topic_id) references sign_up_topics(id)"
  end