human
Solve the following python programming problem given the following code:
@ defer.inlineCallbacks 
def persist_events(self, events_and_contexts, backfilled = False, is_new_state = True) : 
    if (not events_and_contexts) : 
        return 
if backfilled : 
        start = (self.min_stream_token - 1) 
        self.min_stream_token -= (len (events_and_contexts) + 1) 
        stream_orderings = range (start, self.min_stream_token, (- 1)) 
        @ contextmanager 
        def stream_ordering_manager() : 
            (yield stream_orderings) 
stream_ordering_manager = stream_ordering_manager () 
else : 
        stream_ordering_manager = self._stream_id_gen.get_next_mult (len (events_and_contexts)) 
with stream_ordering_manager as stream_orderings : 
        for ((event, _), stream) in zip (_, stream_orderings) : 
            event.internal_metadata.stream_ordering = stream 
chunks = [events_and_contexts [x : (x + 100)] for x in xrange (0, len (events_and_contexts), 100)] 
        for chunk in chunks : 
            (yield self.runInteraction ('persist_events', self._persist_events_txn, events_and_contexts = chunk, backfilled = backfilled, is_new_state = is_new_state)) 

    
    

    Fix the buggy line: for ((event, _), stream) in zip (_, stream_orderings) :
assistant
#Here is Python code to fix the buggy line: for ((event, _), stream) in zip (_, stream_orderings) :
.

for ((event, _), stream) in zip (events_and_contexts, stream_orderings) :