human
Solve the following python programming problem given the following code:
def auth_token_required(fn) : 
    'Decorator that protects endpoints using token authentication. The token
    should be added to the request by the client by using a query string
    variable with a name equal to the configuration value of
    `SECURITY_TOKEN_AUTHENTICATION_KEY` or in a request header named that of
    the configuration value of `SECURITY_TOKEN_AUTHENTICATION_HEADER`
    ' 
    @ wraps (fn) 
    def decorated(* args, **kwargs) : 
        if _check_token () : 
            return fn (* args, ** kwargs) 
if _security._unauthorized_callback : 
            return _security._unauthorized_callback () 
else : 
            return _get_unauthorized_response () 
return fn 

    
    

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

return def decorated(