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: 20220302123642_assignable_to_permission.rb
    path of file: ./repos/openproject/db/migrate
    
    the code of the file until where you have to start completion: #-- copyright
# OpenProject is an open source project management software.
# Copyright (C) 2012-2024 the OpenProject 
    
  def down
    add_column :roles, :assignable, :boolean, default: true

    execute <<~SQL.squish
      UPDATE roles
      SET assignable = EXISTS(SELECT 1 from role_permissions WHERE permission = 'work_package_assigned' and role_id = roles.id)
    SQL

    execute <<~SQL.squish
      DELETE FROM role_permissions where permission = 'work_package_assigned'
    SQL
  end