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: 20151002044617_clean_anime.rb
    path of file: ./repos/kitsu-server/db/migrate
    
    the code of the file until where you have to start completion: class CleanAnime < ActiveRecord::Migration[4.2]
  def change
    # G => 1, PG => 2, R => 3, X => 4
    change_column :anime, :age_rating, "integer USING (
      CASE age_rating
      WHEN 'G' THEN 1
      WHEN 'TV-Y7' THEN 1
      WHEN 'PG' THEN 2
      WHEN 'PG13' THEN 2
      WHEN 'R17+' THEN 3
      WHEN 'R18+' THEN 4
      END
    )"

    # titles: {
    #   en: 'Attack on Titan',
    #   ja_jp: '進撃の巨人',
    #   ja_en: 'Shingeki no Kyojin',
    #   es: 'Ataque a los Titanes',
    #   it: 'L\'Attacco dei Giganti',
    #   fr: 'L\'Attaque des Titans',
    #   zh_tw: '進擊的巨人',
    #   ko: '진격의 거인'
    # },
    # abbreviated_titles: ['AoT', 'SnK']
    # canonical_title: 'en',
    add_column :anime, :titles, :hstore, default: '', null: false
    add_column :anime, :canonical_title, :string, null: false, default: 'ja_en'
    add_column :anime, :abbreviated_titles, :
    
  def change
    # G => 1, PG => 2, R => 3, X => 4
    change_column :anime, :age_rating, "integer USING (
      CASE age_rating
      WHEN 'G' THEN 1
      WHEN 'TV-Y7' THEN 1
      WHEN 'PG' THEN 2
      WHEN 'PG13' THEN 2
      WHEN 'R17+' THEN 3
      WHEN 'R18+' THEN 4
      END
    )"

    # titles: {
    #   en: 'Attack on Titan',
    #   ja_jp: '進撃の巨人',
    #   ja_en: 'Shingeki no Kyojin',
    #   es: 'Ataque a los Titanes',
    #   it: 'L\'Attacco dei Giganti',
    #   fr: 'L\'Attaque des Titans',
    #   zh_tw: '進擊的巨人',
    #   ko: '진격의 거인'
    # },
    # abbreviated_titles: ['AoT', 'SnK']
    # canonical_title: 'en',
    add_column :anime, :titles, :hstore, default: '', null: false
    add_column :anime, :canonical_title, :string, null: false, default: 'ja_en'
    add_column :anime, :abbreviated_titles, :string, array: true

    # title = romaji title
    # alt_title = english title
    # english_canonical = whether title or alt_title is canonical
    execute <<-SQL
      UPDATE anime
      SET titles = hstore(ARRAY['ja_en', 'en'], ARRAY[title, alt_title])
    SQL
    execute <<-SQL
      UPDATE anime
      SET canonical_title = 'en'
      WHERE english_canonical = true
    SQL

    remove_column :anime, :title
    remove_column :anime, :alt_title
    remove_column :anime, :english_canonical
  end