human
Solve the following python programming problem given the following code:
@ defer.inlineCallbacks 
def delete_pusher_by_app_id_pushkey_user_id(self, app_id, pushkey, user_id) : 
    def delete_pusher_txn(txn, stream_id) : 
        self._simple_delete_one_txn (txn, 'pushers', { 
            'app_id' : app_id, 
            'pushkey' : pushkey, 
            'user_name' : user_id, 
}) 
        self._simple_upsert_txn (txn, 'deleted_pushers', { 
            'app_id' : app_id, 
            'pushkey' : pushkey, 
            'user_id' : user_id, 
}, { 
            'stream_id' : stream_id, 
}) 
with self._pushers_id_gen.get_next () as stream_id : 
        (yield self.runInteraction ('delete_pusher', <MASK>, stream_id)) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def delete_pusher_txn(