human
Solve the following python programming problem given the following code:
def _execute(self, transforms, * args, **kwargs) : 
    'Overriding of a method of WebSocketHandler.' 
    def start_tunnel(future) : 
        'A callback which is called when connection to url is successful.' 
        self.upstream = future.result () 
        self.handshake_request = self.upstream_connection.request 
        self.handshake_request.response_buffer = '' 
        self.handshake_request.version = 'HTTP/1.1' 
        self.handshake_request.body = (self.handshake_request.body or '') 
        tornado.websocket.WebSocketHandler._execute (self, transforms, * args, ** kwargs) 
self.upstream = self.upstream_connect (callback = args) 

    
    

    Fix the buggy line: self.upstream = self.upstream_connect (callback = args)
assistant
#Here is Python code to fix the buggy line: self.

self.upstream = self.upstream_connect (callback = def start_tunnel()