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

module Spotlight
  # Generate a sitemap for the Spotlight exhibit content
  class Sitemap
    attr_reader :sitemap, :exhibit

    ##
    # Add all (published) spotlight 
    
    def add_resources
      exhibit.solr_documents.each do |d|
        sitemap.add sitemap.exhibit_solr_document_path(exhibit, d), priority: 0.25, lastmod: document_last_modified(d)
      end
    end

    private

    def document_last_modified(d)
      lastmod = Time.zone.parse(d[exhibit.blacklight_config.index.timestamp_field]) if d[exhibit.blacklight_config.index.timestamp_field]
      lastmod || Time.zone.now
    end
  end