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: update_service.rb
    path of file: ./repos/gitlabhq/app/services/members
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Members
  class UpdateService < Members::BaseService
    # @param members [Member, Array<Member>]
    # return
    
    def post_update(member, permission, old_access_level_expiry_map)
      old_access_level = old_access_level_expiry_map[member.id][:human_access]
      old_expiry = old_access_level_expiry_map[member.id][:expires_at]

      after_execute(action: permission, old_access_level: old_access_level, old_expiry: old_expiry, member: member)
      enqueue_delete_todos(member) if downgrading_to_guest? # Deletes only confidential issues todos for guests
    end

    def prepare_response(members)
      errored_members = members.select { |member| member.errors.any? }
      if errored_members.present?
        error_message = errored_members.flat_map { |member| member.errors.full_messages }.uniq.to_sentence
        return error(error_message, pass_back: { members: errored_members })
      end

      success(members: members)
    end