Called to forget the userid for a request

    Args:
        request: aiohttp Request object

    Raises:
        RuntimeError: Middleware is not installed

async def forget(request):
    """Called to forget the userid for a request

    Args:
        request: aiohttp Request object

    Raises:
        RuntimeError: Middleware is not installed
    """
    auth_policy = request.get(POLICY_KEY)
    if auth_policy is None:
        raise RuntimeError('auth_middleware not installed')

    return await auth_policy.forget(request)