human
Solve the following python programming problem given the following code:
def access_token_handler(self, f) : 
    "Access token handler decorator.

        The decorated function should return an dictionary or None as
        the extra credentials for creating the token response.

        If you don't need to add any extra credentials, it could be as
        simple as::

            @app.route('/oauth/access_token')
            @oauth.access_token_handler
            def access_token():
                return {}
        " 
    @ wraps (f) 
    def decorated(* args, **kwargs) : 
        server = self.server 
        (uri, http_method, body, headers) = extract_params () 
        credentials = f (* args, ** kwargs) 
        try : 
            ret = server.create_access_token_response (uri, http_method, body, headers, credentials) 
            return create_response (* ret) 
except errors.OAuth1Error as e : 
            return _error_response (e) 
return f 

    
    

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

return def decorated(