# File lib/action_view/helpers/form_options_helper.rb, line 397
      def option_groups_from_collection_for_select(collection, group_method, group_label_method, option_key_method, option_value_method, selected_key = nil)
        collection.map do |group|
          group_label_string = eval("group.#{group_label_method}")
          "<optgroup label=\"#{html_escape(group_label_string)}\">" +
            options_from_collection_for_select(eval("group.#{group_method}"), option_key_method, option_value_method, selected_key) +
            '</optgroup>'
        end.join.html_safe
      end