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: 20220622124646_create_flipper_tables.rb
    path of file: ./repos/sequencescape/db/migrate
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

# This migration was autogenerated by `rails g flipper:active_record`, from 'flipper-active_record' gem
# and then tweaked to make rubocop happy.
class CreateFlipperTables < ActiveRecord::Migration[6.0]
  def self.up
    create_table :flipper_features do |t|
      t.string :key, null:
    
  def self.up
    create_table :flipper_features do |t|
      t.string :key, null: false
      t.timestamps null: false
    end
    add_index :flipper_features, :key, unique: true

    create_table :flipper_gates do |t|
      t.string :feature_key, null: false
      t.string :key, null: false
      t.string :value
      t.timestamps null: false
    end
    add_index :flipper_gates, %i[feature_key key value], unique: true
  end