find_template_extension_from_handler

# File actionpack/lib/action_view/base.rb, line 490
      def find_template_extension_from_handler(template_path, formatted = nil)
        checked_template_path = formatted ? "#{template_path}.#{template_format}" : template_path

        self.class.template_handler_extensions.each do |extension|
          if template_exists?(checked_template_path, extension)
            return formatted ? "#{template_format}.#{extension}" : extension.to_s
          end
        end
        nil
      end