instance method render

# File actionmailer/lib/action_mailer/base.rb, line 591
      def render(opts)
        body = opts.delete(:body)
        if opts[:file] && (opts[:file] !~ /\// && !opts[:file].respond_to?(:render))
          opts[:file] = "#{mailer_name}/#{opts[:file]}"
        end

        begin
          old_template, @template = @template, initialize_template_class(body)
          layout = respond_to?(:pick_layout, true) ? pick_layout(opts) : false
          @template.render(opts.merge(:layout => layout))
        ensure
          @template = old_template
        end
      end