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: 20140407091156_unify_interventions_and_events.rb
    path of file: ./repos/ekylibre/db/migrate
    
    the code of the file until where you have to start completion: class UnifyInterventionsAndEvents < ActiveRecord::Migration[4.2]

    
  def change
    add_reference :analysis_items, :product_reading

    # drop_table :product_links

    add_reference :interventions, :event
    add_column :interventions, :number, :string
    add_column :interventions, :parameters, :text
    execute 'UPDATE interventions SET number = id'
    add_reference :intervention_casts, :event_participation
    add_reference :products, :person

    add_column :events, :nature, :string
    execute "UPDATE events SET nature = 'meeting'"
    change_column_null :events, :nature, false
    remove_column :events, :nature_id
    drop_table :event_natures
  end