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: message.rb
    path of file: ./repos/metasploit-framework/lib/rex/proto/sms/model
    
    the code of the file until where you have to start completion: # -*- coding: binary -*-
require 'rex/mime/message'

module Rex
  module Proto
    module Sms
      module Model
        class Message

          # @!attribute message
          #   @return [String] The text message
          attr_accessor :message


          # @!attribute from
          #   @return [String] The from field in the email
          attr_accessor :from

          # @!att
    
          def to_s
            body = Rex::MIME::Message.new
            body.add_part(self.message, 'text/plain; charset=UTF-8', nil)

            sms = "MIME-Version: 1.0\n"
            sms << "From: #{self.from}\n"
            sms << "To: #{self.to}\n"
            sms << "Subject: #{self.subject}\n"
            sms << "Content-Type: multipart/alternative; boundary=#{body.bound}\n"
            sms << "\n"
            sms << body.to_s

            sms
          end