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: shipment.rb
    path of file: ./repos/ekylibre/app/models
    
    the code of the file until where you have to start completion: # frozen_strin
    
  def prepare
    order if can_order?
    return false unless can_prepare?

    now = Time.zone.now
    values = { in_preparation_at: now }
    # values[:ordered_at] = now unless ordered_at
    update_columns(values)
    super
  end