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: rails3.rb
    path of file: ./repos/acts-as-messageable/lib/acts_as_messageable
    
    the code of the file until where you have to start completion: # typed: strict
# frozen_string_literal: true

module ActsAsMessageable
  class Rails3
    extend T::Sig

    d
    
    def default_scope(order_by)
      # T.unsafe is needed here because the default_scope method is defined in
      # different ways in different versions of Rails. In Rails 3, it is a
      # class method, but in Rails 4, it is an instance method. We can't
      # statically determine which version of Rails is being used, so we have
      # to use T.unsafe here.
      @subject.send(:default_scope, T.unsafe(@subject).order(order_by))
    end