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

module Avatarable
  extend ActiveSupport::Concern

  USER_AVATAR_S
    
    def retrieve_upload(identifier, paths)
      upload = retrieve_upload_from_batch(identifier)

      # This fallback is needed when deleting an upload, because we may have
      # already been removed from the DB. We have to check an explicit `#nil?`
      # because it's a BatchLoader instance.
      upload = super if upload.nil?

      upload
    end