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: layout_helper_behavior.rb
    path of file: ./repos/blacklight/app/helpers/blacklight
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

# Methods added to this helper will be available to all templates in the hosting
# application
module Blacklight
  # A module for useful methods used in layout configuration
  module LayoutHelperBehavior
    ##
    # Classes added to a document's show content div
    # @return [String]
    def
    
    def render_link_rel_alternates(document = @document, options = {})
      return if document.nil?

      document_presenter(document).link_rel_alternates(options)
    end

    ##
    # Render classes for the <body> element
    # @return [String]
    def render_body_class
      extra_body_classes.join " "
    end

    ##
    # List of classes to be applied to the <body> element
    # @see render_body_class
    # @return [Array<String>]
    def extra_body_classes
      @extra_body_classes ||= ["blacklight-#{controller.controller_name}", "blacklight-#{[controller.controller_name, controller.action_name].join('-')}"]
    end
  end