human
Solve the following python programming problem given the following code:
@ extensionmethod (BlockingObservable) 
def to_iterable(self) : 
    'Returns an iterator that can iterate over items emitted by this
    `BlockingObservable`.

    :returns: An iterator that can iterate over the items emitted by this
        `BlockingObservable`.
    :rtype: Iterable[Any]
    ' 
    condition = threading.Condition () 
    notifications = [] 
    def on_next(value) : 
        'Takes on_next values and appends them to the notification queue' 
        condition.acquire () 
        notifications.append (value) 
        condition.notify () 
        condition.release () 
self.observable.materialize ().subscribe (self) 
    def gen() : 
        'Generator producing values for the iterator' 
        while True : 
            condition.acquire () 
            while (not len (notifications)) : 
                condition.wait () 
notification = notifications.pop (0) 
            if (notification.kind == 'E') : 
                raise notification.exception 
if (notification.kind == 'C') : 
                return 
condition.release () 
            (yield notification.value) 
return Enumerator (gen ()) 

    
    

    Fix the buggy line: self.observable.materialize ().subscribe (self)
assistant
#Here is Python program to fix the buggy line: self.

self.observable.materialize ().subscribe (def on_next()