human
Solve the following python programming problem given the following code:
def oauth_required(self, method) : 
    "Decorator that starts the OAuth 2.0 dance.

    Starts the OAuth dance for the logged in user if they haven't already
    granted access for this application.

    Args:
      method: callable, to be decorated method of a webapp.RequestHandler
        instance.
    " 
    def check_oauth(request_handler, * args) : 
        if self._in_error : 
            self._display_error_message (request_handler) 
            return 
user = users.get_current_user () 
        if (not user) : 
            request_handler.redirect (users.create_login_url (request_handler.request.uri)) 
            return 
self.flow.params ['state'] = request_handler.request.url 
        self._request_handler = request_handler 
        self.credentials = StorageByKeyName (CredentialsModel, user.user_id (), 'credentials').get () 
        if (not self.has_credentials ()) : 
            return request_handler.redirect (self.authorize_url ()) 
try : 
            method (request_handler, * args) 
except AccessTokenRefreshError : 
            return request_handler.redirect (self.authorize_url ()) 
return self 

    
    

    Fix the buggy line: return self
assistant
#Here is Python program to fix the buggy line: return self
.

return def check_oauth(