human
Complete the below
def addslash(method):

    ''''Use this decorator to add a missing trailing slash to the request path.
    For example, a request to ``/foo`` would redirect to ``/foo/`` with this
    decorator. Your request handler mapping should use a regular expression
    like ``r\'/foo/?\'`` in conjunction with using the decorator.'
    '''
assistant
#Here is the Python code you requested.
    @functools.wraps(method)
    def wrapper(self, *args, **kwargs):
        if (not self.request.path.endswith('/')):
            if (self.request.method in ('GET', 'HEAD')):
                uri = (self.request.path + '/')
                if self.request.query:
                    uri += ('?' + self.request.query)
                self.redirect(uri, permanent=True)
                return
            raise HTTPError(404)
        return method(self, *args, **kwargs)
    return wrapper