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: 20140806082909_prepare_casts_for_other_actor_types.rb
    path of file: ./repos/ekylibre/db/migrate
    
    the code of the file until where you have to start completion: class PrepareCastsForOtherActorTypes < ActiveRecord::Migration[4.2]
  def up
    # add_column :intervention_casts, :actor_type, :string
    add_column :intervention_casts, :nature, :str
    
  def up
    # add_column :intervention_casts, :actor_type, :string
    add_column :intervention_casts, :nature, :string

    execute "UPDATE intervention_casts SET nature = 'product'"
    # execute "UPDATE intervention_casts SET actor_type = products.type FROM products WHERE products.id = actor_id"
    # execute "UPDATE intervention_casts SET actor_type = 'Product' WHERE actor_type IS NULL OR LENGTH(TRIM(actor_type)) <= 0"

    change_column_null :intervention_casts, :nature, false
  end