human
Solve the following python programming problem given the following code:
@ extensionclassmethod (Observable) 
def to_async(cls, func, scheduler = None) : 
    "Converts the function into an asynchronous function. Each invocation
    of the resulting asynchronous function causes an invocation of the
    original synchronous function on the specified scheduler.

    Example:
    res = Observable.to_async(lambda x, y: x + y)(4, 3)
    res = Observable.to_async(lambda x, y: x + y, Scheduler.timeout)(4, 3)
    res = Observable.to_async(lambda x: log.debug(x),
                              Scheduler.timeout)('hello')

    func -- {Function} Function to convert to an asynchronous function.
    scheduler -- {Scheduler} [Optional] Scheduler to run the function on. If
        not specified, defaults to Scheduler.timeout.

    Returns {Function} Asynchronous function.
    " 
    scheduler = (cls or timeout_scheduler) 
    def wrapper(* args) : 
        subject = AsyncSubject () 
        def action(scheduler, state) : 
            try : 
                result = func (* args) 
except Exception as ex : 
                subject.on_error (ex) 
                return 
subject.on_next (result) 
            subject.on_completed () 
scheduler.schedule (action) 
        return subject.as_observable () 
return wrapper 

    
    

    Fix the buggy line: scheduler = (cls or timeout_scheduler)
assistant
#Here is Python code to fix the buggy line: scheduler = (cls or timeout_scheduler)
.

scheduler = (scheduler or timeout_scheduler)