human
Solve the following python programming problem given the following code:
def activate(self, external_subscriptions, observer, deactivate) : 
    join_observers = [] 
    for pattern in self.expression.patterns : 
        join_observers.append (self.plan_create_observer (external_subscriptions, pattern, observer.on_error)) 
def on_next(* args) : 
        try : 
            result = self.selector (* args) 
except Exception as e : 
            observer.on_error (e) 
            return 
observer.on_next (result) 
def on_completed() : 
        for join_observer in join_observers : 
            join_observer.remove_active_plan (active_plan) 
deactivate (active_plan) 
active_plan = ActivePlan (join_observers, on_next, join_observers) 
    for join_observer in join_observers : 
        join_observer.add_active_plan (active_plan) 
return active_plan 

    
    

    Fix the buggy line: active_plan = ActivePlan (join_observers, on_next, join_observers)
assistant
#Here is Python code to fix the buggy line: active_plan = ActivePlan (join_observers, on_next, join_observers)
.

active_plan = ActivePlan (join_observers, on_next, def on_completed()