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: has_message.rb
    path of file: ./repos/postal/app/models/concerns
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module HasMessage

  def self.included(base)
    base.extend ClassMethods
  end

  
    
    def include_message
      queued_messages = all.to_a
      server_ids = queued_messages.map(&:server_id).uniq
      if server_ids.empty?
        return []
      elsif server_ids.size > 1
        raise Postal::Error, "'include_message' can only be used on collections of messages from the same server"
      end