code: def _qr_code(self, instance):
          
          request = self.request # FIXME
          try:
              user = instance.user
          except ObjectDoesNotExist:
              return _("Please save first!")
  
          current_site = get_current_site(request)
          username = user.username
          secret = six.text_type(base64.b32encode(instance.bin_key), encoding="ASCII")
  
          key_uri = (
              "otpauth://totp/secure-login:%(site_name)s-%(username)s?secret=%(secret)s&issuer=%(issuer)s"
          ) % {
              "site_name": urlquote(current_site.name),
              "username": urlquote(username),
              "secret": secret,
              "issuer": urlquote(username),
          }
          context = {"key_uri": key_uri}
          return render_to_string("secure_js_login/qr_info.html", context)
docs: return generate html code with "otpauth://..." link and QR-code