human
Solve the following python programming problem given the following code:
@ extensionmethod (Observable) 
def default_if_empty(self, default_value = None) : 
    'Returns the elements of the specified sequence or the specified value
    in a singleton sequence if the sequence is empty.

    res = obs = xs.defaultIfEmpty()
    obs = xs.defaultIfEmpty(False

    Keyword arguments:
    default_value -- The value to return if the sequence is empty. If not
        provided, this defaults to None.

    Returns an observable {Observable} sequence that contains the specified
    default value if the source is empty otherwise, the elements of the
    source itself.
    ' 
    source = self 
    def subscribe(observer) : 
        found = [False] 
        def on_next(x) : 
            found [0] = True 
            observer.on_next (x) 
def on_completed() : 
            if (not found [0]) : 
                observer.on_next (default_value) 
observer.on_completed () 
return source.subscribe (on_next, observer.on_error, on_completed) 
return AnonymousObservable (self) 

    
    

    Fix the buggy line: return AnonymousObservable (self)
assistant
#Here is Python program to fix the buggy line: return AnonymousObservable (self)
.

return AnonymousObservable (subscribe)