    # File lib/action_controller/base.rb, line 1083
          def expires_in(seconds, options = {}) #:doc:
            cache_options = { 'max-age' => seconds, 'private' => true }.symbolize_keys.merge!(options.symbolize_keys)
            cache_options.delete_if { |k,v| v.nil? or v == false }
            cache_control = cache_options.map{ |k,v| v == true ? k.to_s : "#{k.to_s}=#{v.to_s}"}
            response.headers["Cache-Control"] = cache_control.join(', ')
          end