human
Solve the following python programming problem given the following code:
@ classmethod 
def ApplyAccounting(cls, client, accounting, callback) : 
    'Apply an accounting object. This involves a query to fetch stats and applied op ids,
    check that this operation has not been applied, increment of values and Update.
    ' 
    op_id = Operation.GetCurrent ().operation_id 
    assert (_OnException is not None), 'accounting update outside an operation' 
    def _OnException(accounting, type, value, traceback) : 
        Accounting.ApplyAccounting (client, accounting, callback) 
def _OnQueryAccounting(entry) : 
        if (entry is None) : 
            accounting.op_ids = op_id 
            with util.Barrier (callback, on_exception = partial (_OnException, accounting)) as b : 
                accounting.Update (client, b.Callback (), replace = False) 
else : 
            prev_op_ids = entry.op_ids 
            found = entry.IsOpDuplicate (op_id) 
            if found : 
                callback () 
                return 
entry.IncrementStatsFrom (accounting) 
            with util.Barrier (callback, on_exception = partial (_OnException, accounting)) as b : 
                entry.Update (client, b.Callback (), expected = { 
                    'op_ids' : (prev_op_ids or False), 
}) 
Accounting.Query (client, accounting.hash_key, accounting.sort_key, None, _OnQueryAccounting, must_exist = False) 

    
    

    Fix the buggy line: assert (_OnException is not None), 'accounting update outside an operation'
assistant
#Here is Python program to fix the buggy line: assert (_OnException is not None), 'accounting update outside an operation'
.

assert (op_id is not None), 'accounting update outside an operation'