code: async def forget(request):
      
      auth_policy = request.get(POLICY_KEY)
      if auth_policy is None:
          raise RuntimeError('auth_middleware not installed')
  
      return await auth_policy.forget(request)
docs: Called to forget the userid for a request
  
      Args:
          request: aiohttp Request object
  
      Raises:
          RuntimeError: Middleware is not installed