Internal Server Error

The server has either erred or is incapable of performing the requested operation.

Traceback (most recent call last):
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/webapp2.py", line 1573, in __call__
    rv = self.handle_exception(request, response, e)
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/webapp2.py", line 1567, in __call__
    rv = self.router.dispatch(request, response)
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/webapp2.py", line 1314, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/webapp2.py", line 1138, in __call__
    return handler.dispatch()
  File "/srv/main.py", line 76, in dispatch
    super(SimpleHandler, self).dispatch()
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/webapp2.py", line 606, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/webapp2.py", line 604, in dispatch
    return method(*args, **kwargs)
  File "/srv/main.py", line 94, in get
    self.simple_get('templates/tou.html', locale)
  File "/srv/main.py", line 72, in simple_get
    self.response.write(template.render(server_params))
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/jinja2/environment.py", line 1291, in render
    self.environment.handle_exception()
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/jinja2/environment.py", line 925, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/srv/templates/tou.html", line 84, in top-level template code
    <h2>{{ _("サイトの利用にあたって")}}</h2>
  File "/layers/google.python.pip/pip/lib/python3.9/site-packages/jinja2/utils.py", line 84, in from_obj
    if hasattr(obj, "jinja_pass_arg"):
jinja2.exceptions.UndefinedError: '_' is undefined