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: 20200730205554_create_group_default_tracking.rb
    path of file: ./repos/discourse/db/migrate
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

class CreateGroupDefaultTracking < ActiveRecord::Migration[6.0]
  def change
    create_table :group_category_notification_defaults do |t|
      t.integer :group_id, null: false
      t.integer :category_id, null: false
      t.integer :notification_level, null: false
    end
    
  def change
    create_table :group_category_notification_defaults do |t|
      t.integer :group_id, null: false
      t.integer :category_id, null: false
      t.integer :notification_level, null: false
    end

    add_index :group_category_notification_defaults,
              %i[group_id category_id],
              unique: true,
              name: :idx_group_category_notification_defaults_unique

    create_table :group_tag_notification_defaults do |t|
      t.integer :group_id, null: false
      t.integer :tag_id, null: false
      t.integer :notification_level, null: false
    end

    add_index :group_tag_notification_defaults,
              %i[group_id tag_id],
              unique: true,
              name: :idx_group_tag_notification_defaults_unique
  end