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: 20231020154219_add_trgm_index_to_meeting_agenda_item_notes.rb
    path of file: ./repos/openproject/db/migrate
    
    the code of the file until where you have to start completion: class AddTrgmIndexToMeetingAgendaItemNotes < ActiveRecord::Migration[7.0]
  def change
    # A previous migration 20230328154645_add_gin_trgm_index_on_journals_and_custom_values
    # already 
    
  def change
    # A previous migration 20230328154645_add_gin_trgm_index_on_journals_and_custom_values
    # already enabled on the extension. Hence we do not attempt to enable it here, just
    # to use it if it's available.

    if extensions.include?('pg_trgm')
      add_index(:meeting_agenda_items, :notes, using: 'gin', opclass: :gin_trgm_ops)
    end
  end