    # File lib/action_view/helpers/form_options_helper.rb, line 265
          def option_groups_from_collection_for_select(collection, group_method, group_label_method, option_key_method, option_value_method, selected_key = nil)
            collection.inject("") do |options_for_select, group|
              group_label_string = eval("group.#{group_label_method}")
              options_for_select += "<optgroup label=\"#{html_escape(group_label_string)}\">"
              options_for_select += options_from_collection_for_select(eval("group.#{group_method}"), option_key_method, option_value_method, selected_key)
              options_for_select += '</optgroup>'
            end
          end