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: 020_teams_users.rb
    path of file: ./repos/expertiza/db/migrate_save
    
    the code of the file until where you have to start completion: class TeamsUsers < ActiveRecord::Migration[4.2]
  def self.up
    create_table :teams_users do |t| # maps users to teams; in rare cases, a single individual is on > 1 team for an assgt.
      t.column :team_id, :integer
      t.column :user_id, :integ
    
  def self.up
    create_table :teams_users do |t| # maps users to teams; in rare cases, a single individual is on > 1 team for an assgt.
      t.column :team_id, :integer
      t.column :user_id, :integer
    end
    execute "alter table teams_users
             add constraint fk_users_teams
             foreign key (team_id) references teams(id)"
    execute "alter table teams_users
             add constraint fk_teams_users
             foreign key (user_id) references users(id)"
  end