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: 20210510075720_migrate_outgoing_payment_list_document_nature_change_check_letter_name.rb
    path of file: ./repos/ekylibre/db/migrate
    
    the code of the file until where you have to start completion: class MigrateOutgoingPaymentListDocumentNatureChangeCheckLetterName < ActiveRecord::Migration[5.0]
  
  CHECK_LETTER_NAME = 'Lot de décaissement : Lettre(s)-chèque(s)'

  def change
    reversible do |dir|
      dir.up do
        ex
    
  def change
    reversible do |dir|
      dir.up do
        execute <<~SQL
          UPDATE document_templates
          SET name = '#{CHECK_LETTER_NAME}'
          WHERE nature = 'outgoing_payment_list__check_letter';
        SQL
      end
    end
  end
end